I've driven for 40 years and been a driving instructor for over a decade.

The understanding myself and other instructors have is that when nearing the end of a bus lane, about a couple of bus lengths from the end, if the lane and your exit lane is clear then there's no problem cutting into the end.

​Particularly if you're part of a queue of traffic going ahead where you'll ease that flow. However last year I was given a ticket by Newcastle Council for doing this. It really irritates me that sensible driving seems to be secondary to revenue generation, where authorities treat every inch as a capture zone for their coffers.