"guys flying N-registered heavies into Heathrow with FAA tickets will be getting EASA licences"
No, of course not! As MJ says, the requirement to hold an EASA licence applies to pilots who are operating aircraft based in the EASA countries.
That does include FAA and other non-EASA llicenced "heavy" pilots who are flying aeroplanes based in Europe. A number of my colleagues at work are taking their EASA licences right now and I have also just taken my FAA licence in case I ever need that one. Can't have too many licences as you don't know where the next job will be coming from!!
Happy landings
3 Point