Yeah, the point of the piece in the documentary was that buses can be incredibly efficient if designed from the ground up. They were basically like trains on tires. Had their own dedicated road. Had their own dedicated stops. Buses had much larger doors to accommodate a greater # of people getting on and off at one time. They didn't have to lean down for old people b/c the stops were elevated and the entrance to the bus was at curb level with no steps to go up or down. Stops were less frequent (one of the things that drives me nuts about Chicago buses is that they will stop 5 times over 5 blocks). I agree that most buses in American aren't more efficient than the train. The point in that segment was that they can be wildly more efficient given the minimal expense and with appropriate planning / design.
I remember some city here in britain planning a system like that. Spent millions in planning and then it never happened, or something. Still it's other people's money they're wasting so why should they care.
The DLR (a crappy offshoot of the tube for people unfortunate enough to work in the docklands), is automated, with driverless trains. You can sit right at the front and look out the window as you go along, like the world's worst roller coaster. I've heard it is not as reliable as the rest of the network - perhaps because when something goes wrong there just isn't anyone around to sort it out.