2) Even with self driving, there would be some efficiency gains from a bus, especially in places dense enough that there just isn't space for a car per person, like Manhattan. It would take adding something like 50 lanes of highway across the Hudson River to replace the capacity that trains currently provide for people to enter Manhattan from the mainland, IIRC. Neither electricity nor self driving in any way reduce the amount of space a car takes up. In fact self driving increases traffic by making it easier to go for a drive -- perhaps even send a car out for a 0 passenger cargo pickup trip.

Public transit is here to stay.