Changing routes isn't really that frequent once you have a working setup.

As for intercity travel, this should be set up as rail, not a bus, in basically 100% of cases.

I've been to major European cities in the last few weeks, Paris, London, Edinburgh, all of them, with no exception had bus routes changed temporarily because of construction, protests, events etc. Of course it's frequent.

Most trolleybuses I know have independent emergency propulsion and can reattach without too much difficulty at specific places (usually stops). So temporary short rerouting isn't difficult. Apparently they even have trolley/battery hybrids in zurich where the battery is used as part of normal operation (claiming to need wires only for ~half of the route).