In fact, Prop 1A is a law that can't be changed by the Legislature on its own. Changing its provisions requires a re-vote. The Legislature *could* write the re-vote, which would give it some control over the terms, but the voters would have to approve it. That's why nobody has wanted to do it - the voters would as likely as not just vote down the whole project, while if an argument can be made that some expenditure meets Prop 1A's provisions (that has a chance to hold up in court when challenged, which would occur because of the self-contradictory requirements for HSR embedded in it) it can go ahead and use the bond money). Caltrain electrification made that argument and won. SoCal so far has not put together a package for Metrolink or Union Station (though there are signs of it happening per other comments) to make that argument.