As a Tibetan Buddhist practitioner,I am very surprised that you are linking to that particularly negative article by Michael Parenti, which has no relevance to the question in the OP from Sherubtse or to Retro's question .
The article has been around for a few years on Buddhist forums and is known to be inaccurate and quoted by westerners who choose to despise Tibetan Buddhism. These same people have usually never spoken to either lay Tibetans or even Tibetan Buddhist practitioners at a centre or monastery They instead choose to form opinions from inaccurate secondary source information and from Chinese propaganda.
Michael Parenti is a western historian using secondary and questionable sources and is not an expert on Tibet or Tibetan Buddhism. He doesn't speak Tibetan nor does he appears to have spent any time even talking to Tibetans. Some of the information he cites as Tibetan history is also inaccurate.
You might like to read a response to the article which can be found here:http://www.studentsforafreetibet.org/article.php?id=425
and repeated here at the Canada Tibet Committee:http://www.tibet.ca/en/newsroom/wtn/archive/old?y=2003&m=7&p=23_4
Thank you for your articles Dazzle, however, the question was the protocol (and sometimes historically the lack thereof)amongst various Tibetan Buddhist schools, http://www.tibetinfonet.net/content/update/116
The infusion of political power and propaganda in Buddhism has always led to a downward course:
Historians see the Shugden cult as having flourished under the reign of the Fifth Dalai Lama, Lobsang Gyatso (1617-1682). Although he established the supremacy of the Gelugpa school and was the first Dalai Lama to exert political power over Tibet, spiritually, Lobsang Gyatso was also firmly linked to other schools of Tibetan Buddhism. He felt a particular affinity with the Nyingmapa, the most ancient school of Buddhism in Tibet, and integrated some of their traditions into state rituals. His promotion of Nyingmapa deities to the status of state oracles and ritual protectors drew objections within his own Gelugpa school, giving rise to the first historically verifiable appearances of the Shugden cult.
In the twentieth century, the Shugden cult was propagated from Sera monastery by Lama Pabongka, who was as universally acknowledged for his scholarship as for his recusant attitude towards other Buddhist schools. After 1959, the dominance of the Gelugpa establishment within early Tibetan exile institutions raised strong tensions, threatening to split the community. One of the most influential personalities of the early years in exile, a disciple of Pabongka and fervent Shugden follower, was one of the late tutors of the current Dalai Lama, Trijang Rinpoche. The Dalai Lama, however, is known for having had a more hearty relationship to his other tutor, the late Ling Rinpoche, whose more open and ecumenical attitude strongly influenced him. As time went by, the Dalai Lama reformed the exile institutions to make them more inclusive to different Tibetan groups of various regional and religious backgrounds. He had expressed his reservations towards the Shugden cult for many years, before taking a more clearly disapproving stance in 1996. He has consistently advised Tibetans, and particularly monks, to rethink their attitudes towards Shugden and requested that, if they do not feel able to give up its worship, to refrain from participating in religious ceremonies that he led personally. Although the move created some tensions within the exile community, partly due to pressures exerted on Shugden followers by some over zealous Tibetans, as a whole, these eased over the years, mainly because the most influential Shugden detractors gave up the cult or relocated outside India. Most laypeople, given that the cult was mainly a monastic phenomenon, followed instinctively the advice of their supreme spiritual leader.
Basically, like most schools, sometimes there were periods of fierce competition and periods of amity between the schools, and generally, political power generally destroyed this amity.