That's the word from industry publication Production Weekly, which tweeted earlier today that Franco has the part, and that filming will begin in early March in Utah. The mountaineer, Aron Ralston, was climbing in southeastern Utah in 2003 when a boulder came loose and crushed his arm against the wall of the canyon, pinning him there for several days. Probably something like 125 or 130 hours total, I'm guessing. (You can read all the gruesome, bone-sawing details on Ralston's Wikipedia page.) Anyway, while there are no specifics yet, one assumes Boyle will be shooting in the same general area where the incident happened, which isn't too far from where John Ford used to shoot a lot of his Westerns.
The big question is how a film that is basically a one-man show -- in which that one man is trapped under a rock most of the time -- will be interesting to watch. Franco is a good actor, but does he have the intensity and charisma required to hold our attention when he's the only person on the screen? A lot will probably depend on what the screenplay (which Boyle is writing with his Slumdog Millionaire collaborator, Simon Beaufoy) gives Franco to do while he's lying there. If it involves a lot of grinning and squinting, perfect!