The positive for Nibali is that
Liquigas is the best team in the world and he is the best descender in the world. So like in Vuelta this year they could get some team time on some stage if there are some breaks or something. Since its a Tour with not many opportunities its more likely, but since its the Tour, less likely.
Then theres the descent finish where he can get some time.
I can't see him hold off Menchov Evans or Sanchez in the tt. Obviously not Wiggins but he can get some time on him in the climbs if hes in good form.
Nibali on good form can be a great climber and if he brings that to the Tour Im not sure that even Evans will be able to drop him ( both a year older).
We remember the bad stuff like getting dropped on Zoncolan 10 Giau, Fedaia, Finnestre, La Frapnaga (or whatever) Angliru etc. But there is plenty of great stuff too like Verbier, Ventoux, Grappa, Kronplatz, Mortirolo, Zoncolan 11, Nvegal.
If the latter Nibali comes to the Tour, he could hold on to everyone (bar if he rides, Contador of course).
Its the tts where he could lose time to too many riders, which is ironic because in recent Gts weve seen tts as the places where he is to gain time.
Oh and no Nibali is not an equal time trialist to Sanchez, not yet anyway