Has been discussed here before. Brightline/Virgin doesn't do electric HSR which is what Desert Xpress/XpressWest's project was for. They do 125mph diesel trains.

Also, the Victorville-Vegas route isn't flatland like Brightline in FL; it has actual mountains that the original HSR project was going to poke a tunnel through after running up and down freeway grades (a bit stiffer than the average railroad) along I-15. IOW don't trust a news article with weasel words indicating that the writer was making WAG. Unless they are silently well along in the process environmental reevaluation, permit renewal, and pre-construction work for this are definitely going to take more than 3 years.

Just for fun, read through some of the NEPA stuff (ROD issued in 2011 and so far no indication of an update for Virgin's scheme) at FRA. [www.fra.dot.gov] That'll give you an idea of what Branson's up against. Consider what changes are likely to be needed to substitute a slower diesel for the original electrics, and what might be needed to cut the project cost in half.