I doubt it would ever do so, if it ever was to it would likely be on routes with low demand say Stansted to Manchester Mass, or the likes of JFK to Liverpool and the such. More likely easyJet would do routes with its A321N’s but I don’t see that happening. I do have that at my IAD tho lol.
If there ever was to be one of those routes for Canada I’d say it would be akin to FlyGlobespan who did fly from the UK to Canada, it flew to Hamilton from Manchester and Doncaster with a 757. They also did lights to JFK and Boston sometimes with a 737-800 akin to Ryanair’s fleet via Bangor or Iceland.