You can go via ATL - MPM exceeding is not your problem. That way you can still get superior TK over the Atlantic and not have to fly AC.
Aeroplan can open up any AC flight for you - but the connector within Europe has to have award availability. They will not buy a revenue seat unless last resort.

If you see any other TK available from the US - they can easily open up the short AC connector.

Be prepared with options when you call in. Ideally try to get them to buy you YYZ-IST on TK, but if they refuse (most likely) - tell them to go via ATL, or any other US gateway that has TK available.