i also am trying to travel to the big T this coming summer although not on a bike well maybe I'll take any means possible.This is what my research has uncovered

You need a TTB permit (T i be Travel permit) to enter the big T this only allows you to purchase plane /train tickets and gets you on said plane/train.You can not get this permit by itself you have to book a tour with a company into the big T.If any one sells you just the TTB i would be wary.The TTB just gets you to Lahsa and surrounds.That's it.

If you want to go further you need a PSB permit and once again with a registered travel company but all foreigners need to be of the same nationality.Makes it hard.

In this present environment I think independent travel into the big T will be hard.

The people who you quoted posted along time ago even then one was running checkpoints would you like to do that now I certainly don't.

I have family working there( they work for the Govt tourism as a fact) and they said they can get me in but typically Chinese they said I just need my passport but I am not holding my hopes up on getting in.

Update: just been stuffed around again .Family member who worked at Ali on the checkpoint has retired.Funny his brother told us a week ago he is going to Lahsa for training in August i should go with him.

Man dealing with the Chinese especially my family is doing my head in.