Canadian pilots can and do fly in Europe.
As you know some come across to fly in Europe as part of the agreement, the reason they are not more of them is because Sunwing can't spare them.. So the problem is on the Canadian side.
Many of the other EU airlines have or had expat pilots flying for them for various lengths of time.
The ground staff and cabin staff would not be employed without the European pilots, as Sunwing would have to close or scale back its operations.
The idea that you can have a Canadian guy just flying for the season then going back to firefighting is pretty weak.. You need a current and type rated guy who is flying year round.
Sunwing can't keep these guys on the books year round, so we have the pilot swap or pilot loan situation.