I've often wondered what might happen if Apple, Google, and Facebook joined forces, bought a couple of Tunnel boring machines, and bored a pair of tunnels from Cupertino to San Francisco, right underneath El Camino. If you looked at the number of people carried by private busses between San Francisco and the south bay it would get good ridership. If you threw in access to as much dark fiber as you wanted between those two points and added big fiber drops to PAIX, MAE-EAST and SF, you could offset costs by selling this capacity up and down the peninsula.

I also know if Google built the tube they could figure out how to do it for a whole lot less than the $1B/mile that these things command in the public sector.