I cannot give a definitive answer to your question, except to note that the AC webpage says holders of an Executive Class ticket can enter the lounge.

I don't know if that is unintentionally sloppy writing intended to mean "travelling in the actual J cabin" and excludes the PIT-bound passenger, or if it is intentionally precise writing intended to mean exactly what it says and includes the PIT-bound traveller who is indeed on an executive class ticket and merely seated in the Y cabin.