That's what I've heard, too. The frozen fries he uses are apparently a 100% potato product, with no flavour enhancers or coatings, but they're more consistent than using fresh. I'm sure there's a convenience factor, too, given the number of fries they must go through at Bouchon.
I think Keller uses frozen french fries at Bouchon for the same reason he uses farm raised salmon at the French Laundry, they are consistent throughout the year.
As for storage, my understanding is that there are significant variations by potato variety. McGee says that the starch-to-sugar conversion happens in storage below 45F/7C, but that they can be reconditioned by subsequent storage for several weeks at room temperature. (He notes that potato chip manufacturers do this.) I'm sure there's an ideal level of both sugar and starch to give the right colour and texture, but retail potato options around here are quite limited, and I'm not convinced any of them are ideal for fries.