I live in socal and generally like public transportation but this has always been a terrible idea, for exactly the reason DucatiMonster696 stated above. Sure, a fast train beats sitting in a car, but at that point why not just fly which is 1)already available, 2) faster, and 3) about the same price for a ticket, assuming the train is ever completed?
edit: and if the point is to spend money to get people doing something instead of sitting around collecting unemployment, this ranks near the bottom of useful ways to do that in terms of money spent per person employed