It’s like 2-3 hr drive between the two cities, and at both end you have to navigate auto transport, most likely a rental though maybe Uber would work out but at greater cost for anything beyond a single destination. I would imagine most people would just opt to drive, since they need a car at either end of that line?
LA to SFO would be worthwhile but probably much harder.
Between Sacramento and Merced, and LA and Bakersfield, there will be a "high speed rail bus service". For other parts there will be regional commuter train and bus services.
Then, eventually, it'll become: https://hsr.ca.gov/wp-content/uploads/2021/03/Business_Plan_...
Also, for the Las Vegas link, the terminus is on the Metrolink line so you can take a commuter train from Union Station. People taking Amtrak from points east could get off at the Ontario station and it’s a relatively short taxi/bus ride to the RC terminal (Amtrak uses a different set of tracks coming into L.A. from the east than the Metrolink station serving RC). I suppose it would be feasible to extend the line a little further south to connect with Amtrak should there be demand (if they went to the Ontario station, then the Ontario airport could also be integrated into the service).