Using a web-based calculator I found that KEF-YYZ great circle is 2597 miles. Is that too far?
LGW-YQX is only 2369 miles though - but I think I might have worked it out. I've known other operators to do LGW-YYZ on 757-200s with one stop in Gander - but surely you'd need ETOPS for a LGW-YQX route that was as short as 2369 miles. So without ETOPS does LGW-YQX direct then become too long for the 757-200?
I just had a look at the JMC fleet list and according to their website one of their 757s does have ETOPS capability. So perhaps they originally planned to use this one for this service and now can't for some reason.
Does this sound about right?