The Blavatsky/Tibet connection that should be sought is the Indo-Persian alchemical Tantric tradition (bhutas-suddha) that is shared as the tantric core of Bon (a Central Asian religion from Persian sources that enters Tibet as a heterodox form of Buddhism, called "Bodhism" throughout the region and from which the Nyingmapas break off in favor of the Buddhism presented in the new translations - see Snellgrove's two volume history as well as John Myrdhin Reynolds work and Donatella Rossi's new book on Bon). The Central Asian Dzog chen is common to and found within Bon, Nyingmapa lineage, as well as in some northern Indian elements of the Sikhs, Nathas.
Regarding Blavatsky's oriental sources people seem ignorantly fixated on looking either at Tibet or India without getting current on the history of Central Asian religion. That is the direction and region that one academic reviewer of Paul Johnson's book, who generally praised it, Professor James Robinson (expert on both gnosticism and Tibetan Buddhism - fellow student with Jeff Hopkins, Anne Klein, Wallace, Reynolds and studied under Geshe Sopa) thinks is the place to look for HPB's sources. Paul Johnson's book provide the best historical clues, in light of our growing knowledge of the region, of re-connecting up with any "order" that the mahatmas may have been a part of - if such existed or exists now. The evidence from Tun huang is conclusive. The pudgalavadins, condemned as heretical in India despite being over 80,000 strong even after persecution from the other Buddhist sects, become a form of pudgalavadin yogacarya Buddhism in Central Asia where they survive. This Buddhism becomes the Central Asian Dzog chen attested by the original texts found at Tun huang (now acknowledged to profoundly modify Nyingmapas sense of their own history by Dzog chen master Namkhai Norbu and others) which affirms that anatman only denies a self (purusa) autonomous (atman, related to atom, auto, autonomous) from conditioned co-production and not a continuous person (pudgala bhavana) or personal continuum. It is this source, BTW, that Guenon affirmed was the source of HPB's theosophy mixed and corrupted by 19th century occultism and freemasonry.
Both Bon and Nyingmapa sources affirm, that Dzog chen comes to Tibet from the northwest - from a persiansource (repeated in earlier Nyingmapa sources but affirmed by the great 19 century Nyingmapa scholar and practitioner, Jamgon Kongtrul Lodro Taye) and from Oddiyana in Shambhalla (the Tun huang and Central Asian Buddhist texts recovered by Emmerich and discussed by snellgrove and taught as part of recovered Buddhist history in Dharmasala identify this region as "Shamis en Balkh" - modern day Balkh in Afghanistan where ruins of many Buddhist stupas and monasteries still exist). Tun huang sources also show that a possible Bon is the pudgalavadin version of Buddhism coming into Tibet BEFORE orthodox versions make it in. The Nyingmapas, as also affirmed by Kongtrul and Longchenpo, split off from the Bon when the new translations begin in Tibet. Western scholarship tended to disbelieve this until documentation from original sources and contemporary with the time were found to substantiate it. As the other Tibetan Buddhist lineages have always suspected, Dzog chen is not quite orthodox Buddhism but a heterodox form of it. But whether or not Dzog chen was originally non-Buddhist altogether, heterodox Buddhist Bon or pudgalavadin or whatever). Since nothing in Tibet matches HPB yet nothing in India matches her views either, again, what is the objection to looking in Central Asia except those interested lack the academic or secondhand competence to intelligently look there? Tibetan is an equivocal term. It could mean linguistic, racial, religious, political, or geographical. Tibet had colonies. Some are still under the Dalai lama: Bhutan, Mustang. Neither Buddhism nr Bon exhaust the religious landscape there. HPB says it is northern source and esoteric.
As far as "brotherhoods," Central Asia is replete with them and with legends about other brotherhoods that possess ancient knowledge or wisdom. The examples that come to mind are the Naqshibandi Sufis (whose Golden Chain lineage is in the Caucasus), the Khwajagan, the Ashokhs (bards), and before these, Manichaean illuminati and Zoroastrian Magi. Some legends tell of brotherhoods (usually Buddhist and connected with Shambhalla or Manjusri traditions) partly in other dimensions intersecting this world, so to speak. The idea of brotherhoods possessing ancient wisdom is a central and recurring motif in the folklore of the region. Since Central Asia is geographically and culturally divided, there have been several attempts to unite all traditions as exoteric descendents of a great and hidden primordial Wisdom Tradition. Perhaps the earliest strata of such a view is the legacy of the Indo-European tribal traditions of a shared wisdom they all descended from overlaid and reinforced by Indian (Vedic) and Iranian (Avestan) traditions claiming the same thing (as legacies from a proto-Indo-European culture). This common and shared cultural legacy might form part of the basis for HPB's belief in a Wisdom Religion (that supposedly was the true "Vedic Gupta Vidya" Brahminism or true "Buddhist" restoration of it - if we accept her mindset for awhile).
Next, there is the strata of Buddhism. Buddhism spread throughout Central Asia and long thrived there as the "Wisdom" tradition long before it reached Tibet. Scholars have recently claimed that Bon is indeed, not the indigenous religion of Tibet (which it never claimed to be), but from Central Asia/Persia (as it claims). It certainly incorporates both Buddhist and Zoroastrian materials. And the form of Buddhism of a number of Central Asian tribal groups is really Bon. This second strata, both as cultural legend about the region's past and as living tradition amongst some tribal groups, probably influenced HPB also. Consider:
1. Central Asian Bon/Buddhist groups claim that the large group of Buddhists that were declared heterodox in India and suppressed there migrated to Central Asia. These were the Pudgalavadins (personalists) who qualified the strict anatman view of other Buddhists. There is not a static and self-sufficient self but there is a dynamic person. HPB claims a northern esoteric Buddhism as a source but several have correctly charged that her "Buddhism" seems to compromise the anatman doctrine. Some have suggested that she incorporated Hindu elements into her theosophy. While this might partly be true, it might also be the case that her northern Buddhist source is heterodox. In fact, if this is the case, such a source might have convinced her that the incorporation of Hindu elements was warranted as a reconstruction of an original "Wisdom Religion." This pudgalavadin dispersion seems to be one factor in what was to become Bon.
2. The Bon cosmology with its higher bodies is identical to that of Buddhism and Hinduism except that some shamanic and Central Asian traditions inspired by Zoroastrian, Sufi, and perhaps, Taoist sources add another body (kesdjan or hurqalyi) that is not found in Hinduism or Buddhism but is found in Sikhism, Central Asian Bon, and HPB's theosophy (where it is the astral body).
3. Unlike Buddhism's patriarchal bias, the feminine has a bigger place in Bon. In Zoroastrianism, there is the celestial and feminine Daena (Arm. den, Persian, den) that is the heavenly archetype of the soul. Its twin. Now, both Bon and more orthodox forms of Tantric Buddhism have Dzog chen.
But Bon Dzog chen has a feminine divine source within a strongly and recognizably Zoroastrian mythic framework. When Central Asian Bon "lamas" recite a sutra about origins, it sounds like something HPB's Stanzas of Dyzan are drawn from. And both Bon and HPB's Stanzas posit a feminine source unlike more orthodox forms of Buddhism.
Returning to strata in Central Asian legends and traditions about a "Wisdom Religion"," thirdly came Manichaeanism which became the official state religion of the Uighurian Turks in the region. Manichaeanism was the first explicitly syncretistic and ecumenical religion in history claiming to restore the lost primordial wisdom or gnosis or jnana. Manichaeanism continues to exert the legacy of its influence throughout the region's legends and folklore. I'm told there are still Manichaeans in Central Asia but I haven't met one. But this would certainly reinforce rumors of a "Wisdom Religion."
Fourth, came Islam. Islam's apologetics seems to borrowed heavily from Mani in claiming it was the pure and restored revelation primoridally given to Adam, then to Abraham, and finally to Muhammed. Sufi groups developed this line even more in a way that resembles borrowing from Mani (not doctrine but PR techniques - apologetics). And in Central Asian, brotherhoods arise, such as the Khwajagan and other Sufi orders, that encouraged the idea of brotherhoods guarding secret wisdom.
Fifth, there is an interesting failed experiment that was an attempt to syncretistically recreate the alleged "Wisdom Religion" out of Zoroastrianism, Chaldean Neo-platonic and Hermetic traditions, Hinduism, and Islam under the Mongols that did influence HPB. It failed but one literary product survived. Zoroastrians believed, for a while, that this literary remain was a Zoroastrian scripture. Mesopotamian Jews called it the Chaldean Cabala while Aisors referred to it as the true Chaldean Oracles. As several theosophical and non-theosophical sources note, this book was a big influence in early theosophy. It may be the book HPB says was shown to her. It is the Dasatir. It's cosmology is somewhat disappointing but it sure lends support for a belief in a primordial wisdom tradition perserved by a lineage of masters. But, that is what the Mongol ruler wanted it to do in order to have peace in his kingdom.
Sixth, Kabir and the Sikhs arise and encourage and reinforce this same mindset that all faiths descend from one Wisdom Tradition. Sikh groups certainly stilled believed this in HPB's time and were politically engaged in a way that HPB might have sympathesized with and maybe misread. But some Sikhs combined the Buddhist/Hindu cosmology of higher bodies with the idea of an emotional body of the imagination drawn from Sufi and Central Asian sources (the hurqalyi through them, I hypothesize, becomes HPB's astral body).
The idea of a "great white brotherhood" does not seem to exist outside TS circles nor before HPB.
The other thing I would add is that HPB's own way of conceptualizing things seems to have a heavy dose of freemasonry combined with the perspectives and expectations of a Russian aristocrat. So even her own real views about Central Asian brotherhoods may mislead the historical investigator interested in researching them. Godwin's book brings out an aspect of Theosophy that reveals the Euro-centric biases of its founders. Unfortunately, he restricts his attention to Britain. There were (are) two major politico-religious tensions in the region that HPB might have ironically been both sensitive too and misperceived because of her own background. First, within Imperial Russia, there was a major tension between the Muscovy project of rapid modernization and westernization of the Russia Empire, and the more oriental politico-religious and ethnic factors that resisted this 300 year project of the Romanovs. Within the Romanov project, there were contending elements between the Russian Orthodox Church, atheistic secularists and positivists, and the religious "enlightenment" groups associated with Freemasonry. Eventually, it will be due to the mass discontent and social upheaval caused by this project that will lead to the rise of the Bolshies, also lead to their downfall, and now faces Russia today. Anyway, the religious "enlightenment" more or less tied to Freemasonry was a formative influence on HPB that might ave given her a somewhat misguided perspective on things political, religious, and oriental. The second major tension was between the Russian Empire and those ethnic groups who did not want to be part of it whether they were inorporated in it or not. Today, we still see breakaway republics. Just look at the internal campaigns that engaged the Russian military at the time. The Caucasus was the location of a protracted war between Imperial Russian forces and the Muslim Cossacks of Shamil (a Naqshibandhi Sheikyh, btw). Central Asian is not a political unity. Never was. Groups that cooperated with Russia were usually trying to keep Turks or Brits at bay and vice versa. Brotherhoods that were politically active were seeking independence and not a part in a pan-Euro-centric religious "enlightenment." Most brotherhoods were not politically active but rather were sanctums against the on-going violence and vicious round (i.e., samsara) of history as wars, rumors of wars, and peace as temporary subjection to an alien power.
So, HPB, despite her sympathies with Asian religions, peoples, and brotherhoods, might have partly misunderstood the political dynamics and objectives of even her sources and supporters. I mention this for two reasons. I think both the invention, and eventual disappearance of "support" from a "higher source" of the TS reflects HPB's reading and misreading of the nature of Asian brotherhoods. Second, her freemason spectacles may not only reinforce the picture of the masters and great white brotherhood of the "true believer" in the TS, but also, may mislead the historical investigator. If it is assumed that the sources of HPB is being sought fits the freemason template, the thing to be found might be overlooked. If such a mindset was how HPB saw things herself, it might be one of the factors in what seem to be her political misreading of the prospects of the TS. The freemasons might have been a very effective "political" network in Europe and Imperial Russia but Asian brotherhoods were not and likely disinclined to such a project. The Sikh connection that has been made is good. The Sikh's were engaged realizing objectives that coincided with those of HPB, at least, for a while. And some lineages within Sikhism combine both Hindu/ Buddhist and Sufi cosmological elements in a way that closely resembles the cosmology of HPB (see my comments on higher bodies for one bit of evidence). But from a non-Euro-centric perspective, the TS looks too much like western Enlightenment a la Freemasonry style. HPB's astral realm, as noted by scholars and Buddhist as well as Hindu scholar-practitioners, is not found in Buddhist nor Hindu theory of planes (bhumi) nor bodies (sarira) nor sheaths (kosa). She added that. The astral plane of Theosophy comes from Muslim sources, in fact, Sufi Sheikhi illuminationist sources where it is called Hurqalya (Latin, medio mundi of Hermeticists) and the astral body (Latin, caro astralis of Hermeticists, okhema symphyes of the theurgic Neo-platonists) is hurqalyi jism. This addition is rejected by Buddhists and Hindus. There is the physical body (stula sarira) with its two sheaths (the chemical crust or food sheath - annamayakosa and vital sheath - pranamayakosa). Next, where HPB's astral body should be (which both Buddhism and Hinduism reject) there is nothing. Instead, the next higher body is the subtle body (suksma sarira) with its two sheaths (the lower mental or manomayakosa and higher mental-intellectual or buddhimayakosa or vijnanamayakosa). Finally, there is the causal body (sarira karana), which in the unenlightened state, has the blissful ignorance sheath (ajnanamayakosa or anandamayakosa that is also the alaya vijnana as the depth dynamics of ignorance) but is to be replaced, in enlightenment, with the trikaya. The only traditions that use this scheme of planes (bhumis) and corresponding bodies (sariras) AND WHICH HAVE an added astral plane and astral body between the physical body and its two sheaths and the subtle body with its lower and higher mental sheaths BESIDES THEOSOPHY is Central Asian Bon Dzog chen (the Kalmucks and Mongols, with whom HPB had early contact, add astral component based on their residual shamanic traditions and practices that are incorporated within their brand of not quite orthodox Buddhism) and some aspects of the Sikh religion (that incorporated Hindu, Buddhist, and Sufi material). So, if one wishes to not say HPB made it all up, or that she did a botched job of interpreting Hinduism or Buddhism teaching on planes and bodies, but instead, wishes to search for historically verifiable sources (and one isn't a true believer in white brotherhood, but agrees with K.P. Johnson's evidence from HPB herself that she masked her teachers identities by making them bigger than life) then the fact that it is only the Central Asian and Sikh traditions that combine the Hindu-Buddhist scheme with a shamanic-Sufi astral plane and body should indicate to any rational investigator that her sources might come from these traditions.
Another source of HPB is her self-education that both gave her valuable clues and, I suspect, somewhat jaundiced views because she got them out of a private Russian library early. From peasant stock, Gurdjieff, by contrast, may seem much more egnimatic but his language and mention of groups is readily identifiable by those from the region. So, the sevenfold source of both HPB and his cosmology is clearer in his case. So are some of his historical identifications. The Asholkhs are well know bards of the region. And so is his terminology. For example, parkt i dolg is Zoroastrian in origin but became sort of a linqua franca in the regions religions.
The root, which appears in other G words, is ar- related to artha (asha), rta (Vedic), and others. Parkt means glorious vocation or obligatory destiny for a being of a certain ontological dignity. "i dolg" is genetic case for slang for karmic making (i.e. dokan in Armenian) or making ones destiny by meeting one's obligations to the max. G's kesdjian body is the kes i jan crystalline vajra body created by parkt in Armenian and Central Asian Zoroastrianism and Buddhism. So of both HPB and G sources are the folk traditions of the region. And G shares a more realistic view of brotherhoods as confederations of cooperating orders, some very old and prestigious, but not the luridly Peter Pan-like fantasy of ascended masters as a new polytheism.
Theosophists want bedtime stories. And ascended, they all masterfully were above it all blissfully ever after.