Well for when drivers thatare waiting for for express they will usually always make them want for a bus to come in. On the other hand local it's where some will get cut, each depot got a list for school trips which are OK to not send out if no availability.
And it's very common for dispatchers to have to call into maintenance to get a bus released even if it's only for one trip to make service.
As far as why so much OT, not sure.... Maybe the TA has high hopes everyone wants OT but can't force people on it. They have the manpower if they add another trip in everyone's run, not that I want more work lol.
But I assume you know all this by now lol I don't try to talk about stuff I don't know.