I made some more detailed comments in the transit thread, but I think LRt on foothill is a political firestorm that will never have the needed support to actually get done. When you head further south past SLC boundaries, it gets even worse. Not so much due to the train, but primarily due to the increased densities.
A heavy gauge train up Parleys is great, the cost would be astronomical and I just don't see the ridership justifying the cost. I read somewhere a few years back that the average family of four vacationing and skiing at Park City Mt. Resort spend about 8,000 on their trip over 4 days. Spending a few hundred dollars on a rented SUV for that time is probably not going to be much of an issue for them. I don't think tourism in Park City could justify building a rail line. even the rail line from Denver to Winter Park lost money every year, I think it may even be out of service right now. Obama's stimulus plan is for projects that are ready to build. This would have years of EIS work prior to ever getting design dollars.