Since it transports people from Vail to a sparsely populated area in the west whilst the other has to go down to Colorado Springs before going north to Denver in the east, hence the need for a wholly new rail line to Denver to make a Vail Ski Train work. How much skigoers does Vail get compared to Winter Park? Given that the Winter Park Ski Train performs well enough, I think a Vail Ski train would work.
The whole point of an I-70 rail line is to relieve traffic on I-70 between Denver and the Rocky Mountain towns, since
congestion has gotten pretty bad, and I never assumed it would outright replace the Bustang service. Seems the best option would make it part of a greater project.