The other day I was following a bus. He put on his four way flashers and pulled completely off the road into a bus stop, so I proceeded to pass. When I was beside the bus, he pulled out and I had to swerve to avoid a collision. They do have a yield sign on the back of the bus, but don't they have to re-enter traffic just like anyone else on the road?
On any road in British Columbia where the speed limit is 60 km/h or slower, you must yield to a bus that is displaying the prescribed yield sign and is signalling that it wants to move out of the curb lane or bus stop.
That said, the driver of the bus must not move onto the travelled portion of the roadway unless that movement can be made in safety. There are two rules in the Motor Vehicle Act requiring this, one specifically for a bus such as this one and one for all traffic in general. The bus must be granted right of way and the driver was wrong to force it.
It is also possible that the driver failed to identify you as a hazard, either because he did not look or looked but did not see. In your case this was a single laned roadway and you had no option but to pass by carefully. Had it have been a multiple laned roadway, you might consider that something like this could occur and move to the left lane before passing the bus.