There have been several proposals I think. Last I heard it was dead. The problem is that it kind of sucks as a commercial proposition. A Hyperloop solution, on the other hand, wouldn't. I've done a basic profitability analysis on the route, will publish as soon as I can bloggify it. Basically, even with the existing air traffic only, it's a really attractive route, especially if you link it in to an SF-LA Hyperloop as well and hence capture the SF-LasVegas air traffic too.

The main problem with the xpresswest train is that it basically went from nowhere to nowhere. Still needed a car at both ends. That and its being grossly expensive.