I don't think that it is that clear cut.
Norway is a member of the EEA which buys it the right to the deregulation within the EU. The UK on Brexit would not be in either the EU or EEA. EEA and all trade deals would have to be negotiated. There is absolutely no reason whatsover for EU governments to allow a non EU airline rights to compete with EU or EEA airlines.
Brexit is actually a very foolish idea unless you're a banker whose missing his bonus.