id be genuinely surprised if the energy losses of the cables are more than the energy losses of charging the batteries even if they are they are more than likely offset by the weight difference of batteries vs the weight of the cable connecting mechanism.

Then there is the issue of range and the uptime of the vehicles while you can use a trolley 24/7 you have to charge the bev buses

Then there is the issue of extreme weather cold or hot where due to AC and or heating and the temperature itself affects the range a lot

Then there are the maintenance costs of the battery the power capacity since you need space for the batteries

So all in all you exchange a bunch of negatives for the benefit of not needing overhead cables

A trolley with a small built in battery for those last few miles you might need to connect but don't want to pull cables is the best of both worlds.

Hope that was a comprehensive enough dismantling.