Possible but unlikely.
The management of each airport is allowed to operate independantly of each other in virtually every commercial aspect and individual Airport Directors are expected to justify their profit or loss accordingly.
This is true but I doubt that it has been agreed entirely locally, MAG is learning to flex it's combined muscles with airlines. I think it was a case of if you want to fly from MAN then fly from BOH and HUY too. (not sure about EMA tbh)
Each airport is independent but they enjoy group backing especially commercial. And other aspects for that matter.