Вот из авторитетного сит61.
http://www.seat61.com/Nepal.htm#Kathmandu%20to%20Lahsa%20by%20busWeekly Nepal-Tibet bus service? Since around 2005, the internet has been full of reports of a Kathmandu to Lhasa bus service starting, then being withdrawn, then starting again. However, the most reliable information suggests that there is indeed a weekly Kathmandu-Lhasa bus service, running since April or May 2010. It's possibly open to foreigners, but possibly not. Departure day & time from Kathmandu are not known, but in the other direction it leaves Lhasa every Friday at 10:00. The fare is 520 RMB, children under 140cm half price. It's a 955km trip, but journey time not known. If you find out any more, please email me!
А вот и этот автобусик. Вроде как был перерыв, но с прошлгого года опять должны были поехать.
http://vistet.wordpress.com/2010/02/21/kathmandu-lhasa-bus-line-starti ng/