Is the rule against collateral attack applicable?

Notwithstanding the rule against collateral attack is inapplicable, the doctrine of abuse of process must be considered. As Arbour J. went on to observe in Toronto v. C.U.P.E. at para. 37: ... Canadian courts have applied the doctrine of abuse of process to preclude relitigation in circumstances where the strict requirements of issue estoppel (typically the privity/mutuality requirements) are not met, but where allowing the litigation to proceed would nonetheless violate such principles as judicial economy, consistency, finality and the integrity of the administration of justice.