> Even with dedicated lanes (which is costly and unpopular) they still need to go around obstacles like buildings, follow the roads, yield to pedestrians, pull into stops, etc. Speed limits need to be obeyed as well.

In this case, Buses can drive in the underground tunnels that were built for this subway, can't they? Seattle did it for many years until they replaced it with trains: https://m.youtube.com/watch?v=etT_wVuKy_I

In that case, the only thing slowing down the bus is speed limits, which are probably a bit lower than a train, since train would be safe on rails, but still I wonder why they didn't use that given that the tunnels are here and in good condition