ILS25
The BFS-EWR flight almost did disappear last year. Some last minute scrambling by government kept it going.
Look the fact is the airlines obviously don't think having a DUB-YYZ/JFK/ORD etc etc running simultaneously with a service from BFS would be as profitable as serving DUB and somewhere else. Airlines only have a finite number of aircraft and crews. A BFS-YYZ may well make money, but would it make more money than an extra CDG/LHR/FRA etc service to YYZ? And would those Airlines' DUB service still be profitable without the pax from North of the border? What about cargo? What about the pre-clearance for the US flights? That's a big enticement too.
Airlines are far more risk averse than they were pre 08. They will take the safer option every time now.