There is way more too it than just innervation. Parapalegics (spell check) have the highest cross sectional area of type II fibers when compared to other populations... including elite athletes.
In terms of distribution, no one on earth has every been anywhere near 80% for fast twitch fibers. Maybe if you are talking about cross sectional area, 80% could be possible in extremely elite athletes, with perfect diets, and superior genetics.
Fiber types can't change. They can take on characteristics of other fibers but no amount of training will actually shift a type I to be a type II. The only way the distribution of fiber types could change is if new fibers are made. This means hyperplasia would have to happen. Even thought, personally, I think it can happen, it's never been shown to happen in humans.