Looking at the maps they produced, a "fast" transit--I imagine that is a high speed train-- running past the three PC resorts (soon to be two, but Canyons will have a separate station) and into BCC and LCC would eliminate a lot of traffic. How costly is the transit? That remains to be seen, and could have a lot to do with the next presidential election since federal funding would likely be in the equation. They are looking out to 2040 with the assumptions of population and other growth, which is reasonable.
The below is not the fast train envisioned:
^^ Yea, I know you guys are too good to ride a bus.
Cost: a couple billion.
To restate in a more clear manner: regardless of the public transportation (unless it is deep up in the canyon), there aren't many people up there. In April, even on good days, Alta is like a ghost town. It is going to be hard to justify spending billions for something fixed and for minimal traffic coming from PC.