I've noticed some road markings lately that allow motorcycles to ride in bus lanes and 2+ occupancy lanes. Does a Motor Tricycle count in this case? They are treated as motorcycles for MSVA, for Vehicle Excise Duty and for rules regarding display of number plates.

As the sign says 'motorcycles' not motor-bicycles, then you could argue that legally a motor-tricycle comes within the definition of a motorcycle. So does a quad-bike.

Try it..... let us know how the court hearing goes.....