I'm surprised at his numbers. He claims a bus costs something like $1/mile, while his car would be something like $0.20/mile. I'm guessing the main difference is the driver, so I wonder if something like the robovan (looks stupid IMO) would be able to replace buses in many cases. In my area, we have on-demand transit outside of bus service zones (a van will come pick you up), so it would be cool if this type of service could connect individual riders to transit hubs.
But yeah, it's not going to be ready in two years. Could be cool though if it is and is priced as he stated (big doubt).
I assume the figure was amortized across typical passenger loads. So if a bus typically carries 10 people, $10/mile to operate becomes $1/mile/passenger. I think that's what Musk is quoting here. I don't know where he gets that figure, but if it's accurate (big doubt) and if he can beat it (again, big doubt), then that's absolutely amazing!
I tried looking for figures, but most of the numbers I see are revenue per passenger, not operating cost per passenger. Revenue isn't particularly interesting because so many transit systems heavily subsidize mass transit.