And the Aerotrain failed because it was (a) underpowered and needed a helper up Cajon on the eastbound trip, and (b) the bus-body cars were notoriously rough riding and felt cramped to passengers more used to PS and Budd standard size cars.

I'd like to see rail service to Vegas again. It was tried in the mid-70s and failed, but back then traffic going up the I-15 & I-215 was not what it is today either. One train a day isn't going to be sufficient to get people to consider it as a viable option. You'd have to have 3 or 4 trips each way at least (leaving from each end at say, 8:00 AM - 11:00 AM - 2:00 PM and 5:00 PM) to present enough choices to make it attractive.

The big stumbling block would be UP. They'd probably insist that Cal Trans pay for all sorts of upgrades before they agree to let the LASL line be used again for passenger trains.