The point is incompatible gauge prevents, discourages repurposing. Of course that was the SP's intent. It worked.

The BART broad gauge empire is sitting on ROW's that could be used by standard gauge OC rail such as CAHSR or a stadtbahn-RER concept which is what Caltrain on the Peninsula is morphing into slowly.

So BART is preparing to launch the final offensive on colonizing Livermore and Tracy is next. Outside the District? - no problem for the Party patronage machine which runs the whole blinking State. In that legendary smoke-filled room BART sits at the table in between Pelosi and Brown. It is the Pet of all Pets, especially the BART unions. How do you think a total piece of transport crap gets to keep blowing billions with aplomb?

Start the BART re-gauge - lord knows the Bay Area loves to spend money on stuff and eventually the standarization will pay off. And WTF is an NYC subway gestalt doing out amongst the farflung farms?