Boston had newish hybrid deisel trolleys until 2023, when they replaced with battery electric buses.

They claimed the catenary was too expensive to maintain, especially with roadwork. Meanwhile the battery electric buses are completely self-contained, independent, and there are multiple manufacturers.

I’m sure it didn’t help that they were over complicated. This was a new transit line where everyone wanted a subway, but it was too complicated. They needed more capacity than a bus, able to maneuver tight corners, electric to go through tunnels, and unconstrained in traffic. They created Frankenstein monster and called it “bus rapid transit”. Partly dedicated roadway, partly in traffic. Partly above ground, partly below ground. Partly deisel, partly trolley. Bigger than buses but articulated to fit through narrow streets