Huh, I'm surprised Canadian courts allow (or allowed?) that. The US won't let you just sue foreign governments in its courts like that.
Exceptions for commercial cases–when a foreign government directly engages in international trade or commerce–are widely accepted. This case falls into that category, so Canada was not being particularly exceptional in allowing it.
Exceptions for human rights abuses, torture, terrorism, etc, are much more controversial. The US legal system is actually a bit of an outlier here (albeit not uniquely one) in being willing to entertain lawsuits against foreign governments on the later bases when most legal systems will not permit them.