It's not really "provisionally positive", it's "actually positive and provisionally suspended". Bad news if it is the case. Given the length of time since the Tour I think it's safe to assume that both the A and B samples tested positive. For me the interesting fact is:
"From the time of the first communication from the UCI, August 24, Alberto Contador alleged food contamination as the only possible explanation of what happened and has been turned over to the cyclist authorities since then in the confidence that this very serious problem could be clarified, which now is public."
(from http://www.cyclingnews.com/news/alberto ... lenbuterol
If the stage in question was July 21st and ythe UCI knew of the results on Aug 24th, then why are we finding out about on Sep 30th via the rider's press conference?? What the f**k sort of standard procedure is that for the UCI to follow? It doesn't matter if it's a tiny amount - if it's positive then it should be announced as such at the time, and the usual processes start up. If it's a trace amount due to contamination then that will emerge and the rider duly exhonorated.
The UCI is not at liberty to pontificate at their leisure as to whether and when a given rider's positive test should be announced. If a rider tests positive then the rider should be notified as soon as possible - which happened - and the test result subsequently made public - which did not.
It's a clear confict of interests that the body responsible for growing and developing the sport worldwide is also charged with running the anti-doping programme. They were happy enough to announce Li Fuyu's positive for the same substance with alacrity earlier this year. Granted the amount was higher so they could argue it's a clearer case, but that's missing, if not outright avoiding, the point.
The UCI has no business in running cycling's anti-doping effort. The pity is that WADA is a toothless tiger by comparison, and national bodies largely toe the UCI line.