Last I heard or read:
Some sort of environmental study had to be done(was it ever completed?)and UP was balking at the idea. Add to that the heavy, frequent, and fast bus service to Vegas and I wonder if it's worth spending the money?
Would the train be fast enough to compete with cars and buses? Unless it was as fast or faster, you'll never get people to take the train to Vegas.
Considering the huge traffic jams that often occur on I-15, the train could compete quite nicely as long as UP doesn't torpedo it, after it leaves BNSF tracks. Throw in a few track improvements to get the speeds up to 90 MPH or even 110 MPH for part of the journey and there would be no competition from the buses.
At present the two biggest problems for LV service are Amtrak's no new services clause in their funding from the Fed, and UP. There were studies done years ago and they all passed. There were even track improvements done on the UP, paid for by Amtrak and others while those studies were on going. By the time everything was in place to start up a service, UP decided that the line was too busy and demmanded more improvements, which killed the service resumption.
What's needed right now to get this back and running is a cooperation agreement between the LV casinos and Amtrak, much like NJT just signed with the Atlantic City casinos. With some backing from the Casino's, as well as packages being offered by the casinos, getting service restarted would be a no-brainer. Sadly, at least so far, the casino's don't see the need to spend the extra money. Hopefully though, the NJT AC service will be a hit and LV will wake up and smell the coffee.