I'm sure many of us have imagined how BART's transition to a system run by one or many competing providers may be logistically difficult and hard to sell to the public. The transbay tube is closed late at night, and I don't know if that's for maintenance, but if it's available during those hours, a private company could make a lot of money if the transit authority would allow private trains on otherwise empty tracks, if only between west Oakland and Embarcadero. It would be popular with riders and businesses who watch so many customers flee to the East Bay before midnight. The company could charge what they wanted, and still be cheaper than a $40 cab ride, and safer to doze off on than the all night AC transit. And it would give the public a chance to compare the types of service they get from a private and state run transit system.
This may be impossible, not just politically, but also logistically, but its sure fun to think about, no?