Motorcycles in your bus lane

Mixing speeds is a non-point. The majority of routes I use (and I'm sure others) don't have bus lanes. I 'mix speeds' all the time.

That's not wrong, but you also want to have a certain logic to speed distribution on the streets. Slowest outside, faster inside. Pedestrians walk on separate footways. Then you get cyclists, who can move aside if necessary (naturally not as a default, but when it's appropriate. Buses stop a lot and are next in line. Taxis are permitted in most London bus lanes and already upset that hierarchy somewhat. If you then mix the very high burst speeds in that are often achieved by motorcyclists, you're likely to change this further. The study of the recent trial also found that motorcyclist speeds increased during the trial.