> It would take years to make a single new bus route in any city, I don't think I've ever even seen that happen.

I live in a city in a Western European country which adds multiple new bus routes a year, and always has done. Honestly I'd assume this is the case for any medium to large city.

The unusual bit about the Shanghai initiative is that, presumably, they have significant _spare_ capacity, to be used for low-volume/experimental stuff like this. Spare capacity is a slightly weird thing for a bus network to have; they tend to run basically on the edge.