Not sure if the local authorities specify what or who can use bus lanes...
They introduced a bus lane through Peterborough several years ago while some long term major roadworks were ongoing. It specified buses, taxis and cyclists (and perhaps motorbikes).
Why taxis ? The whole idea of a bus lane is to encourage public transport, with a view of course of getting cars off the road. Taxis ? they invariably only have one passenger....so its effectively a car, same as the rest of the traffic. That used to pee me off.
At the time (the bus lanes have long gone now) there were taxis, private hire, works minibuses, motorbikes, cyclists...and of course the odd car.
It was still better than using the road normally...but it could have been better still.