I was Motorcycle coordinator for the ACTC for about seven years. And almost every Club had its own class structure. So I managed over a year or two to get it standardised.
No the MCC does not have a sub 150cc Class however those bikes are few and far between.
We do have to remember that it is after all a competition not a green lane fun day out and competitors should pick suitable machinery. (There is no Sub 150 class in the Moto GP.).

Only the MCC does not have this split. It does however follow the standard format in classes for cars...….