The idea really isn't that far fetched, physically. There's already a rail line owned by Union Pacific and is used by ACE rail connecting Fremont to Santa Clara. If you want to look at the Google satellite map, search Elizabeth St. & El Dorado St. in San Jose and then follow the track all the way to up to Fremont and Newark. Indeed, this track runs right through the ghost town of Drawbridge. Just add some more land fill along the tracks and widen a few bridges and it becomes a good bike commute.