Motorcycles in your bus lane

Arguing over percentage points of blame doesn't help any of us work out how to reduce the chances of this happening again.
If the car driver had looked and signalled it might have made a difference, if he did look and saw the cyclist he may not have registered that the motorbike in the distance was coming at twice the speed. We also need to consider that in many modern cars the 'blind spot' for a car driver to the left rear is far bigger than that for a lorry driver.
The motorcycle rider may or may not have been breaking the speed limit (most do) but 30mph is far too fast for safe riding on the left side of a traffic queue. Even if he saw the car's signal it is unlikely that he would have had the time and space to get out of the way.
Both the driver and rider could have behaved in a sensible way that would have avoided the crash. Both are 100% responsible.
The clear outcome from allowing motorcycles into bus lanes is that that they ride faster, have more crashes and the injuries are more serious.

Now, if you will mention motorcycles speeding, I shall mention that when the police followed the speeding assertion by the LCC was it found that on the observed stretches of road that motorcyclists weren't speeding but cyclist were caught breaking the highway code.

The clear outcome is your opinion.