Earlier quoted context omitted.
Streetcars are always less mobile buses. You can do everything you suggest for buses and get the same benefits plus everything that being a bus offers you.
The advantages to streetcars aren't limited to what I suggest. They also include noise and air quality advantages (hooking up to municipal power sources instead of carrying their own engines), human advantages (they tend to be more comfortable than buses, both because of road quality and size), capacity, and so forth. There are many, many situations where buses (ideally, electrified ones) are the right choice. But th…
You can do that with a bus
>they tend to be more comfortable than buses, both because of road quality and size
(1) You can make bigger buses if you want
(2) There's little difference in a streetcar on a track and a bus on a flat road. And it's a lot cheaper to get flat roads than to lay track