YYJ-YYC-YHZ-GLA is only an hour slower than the quickest route which is YYJ-SEA-KEF-GLA, but crossing two additional borders and having to arrive earlier for US pre-clearance will eat up much of the time saving and add risk to missed connections, especially as WestJet and Air Canada are the only airlines that can provide an end-to-end journey on their own metal both taking about 15.5 hrs, all others require codeshare.