It will allow you to fly your legacy A2 within 150m of residential, commercial, industrial and recreational areas (and inside these areas) for 2 years from 1 January 2021 (but not within 50m of people). Unless the rules change. Or the new regs are delayed again. etc.
Without the A2 CofC, you will be able to fly your MA2 pretty much the same places as today i.e. at least 150m outside “congested areas”, although the definition is reworded at the end of the year (“residential, commercial, industrial and recreational areas”).