What is the test for an implied waiver of solicitor-client privilege?

The question of whether privilege has been implicitly waived requires identification of matters of substance by reference to the material facts and the law that governs the client’s claim or defence, as well as an examination of considerations of fairness and consistency, and any litigation advantage that may arise from the enforcement of the privilege. That assessment takes place in the context of the legal standards that govern the rule of solicitor-client privilege. Thus, whether there has been an implied waiver of privilege is a question of mixed fact and law, reviewable on a standard of palpable and overriding error: Housen v. Nikolaisen, 2002 SCC 33 at para. 36, [2002] 2 S.C.R. 235.