The record for the climb in the road stage is a bit over 16 minutes and I don't expect anyone to be significantly faster than Cavagna pre-climb, so the best time would probably be something like 55 minutes at a guess.
TDF 2012 wasn't an ITT, no. I think it was the first time it was in the TDF, or at least in a long time.
I will always remember this stage, as Jurgen Van den Broeck had a puncture about 12k before the finish (MTF), and Lotto gave zero f*cks and nobody waited for him
He lost 2 minutes there, but "luckily" he missed the podium by 4 minutes, so it wouldn't have made a difference.