Can an estoppel by res judicata be raised?

As outlined at para. 29 of Saggers v. Calgary (City of), supra: An estoppel by res judicata cannot be raised unless: (i) there was a final decision pronounced by a court of competent jurisdiction over the parties and the subject matter, (ii) the decision was, or involved, a determination of the same issue or cause of action as that sought to be controverted or advanced in the present litigation, and (iii) the parties to the prior judicial proceeding or their privies are the same persons as the parties to the present action or their privies.