You can access any lounge that permits Star Gold access, which all Maple Leaf Lounges (MLL, or "AC lounge") permit, so long as you are ticketed on a same-day Star Alliance flight.
http://www.aircanada.com/en/travelin...ounges/tc.html has the full Terms and Conditions specifically for MLL, point 2 of which states:
Eligible lounge customers must present their pass/membership card and a confirmed same-day ticket or boarding pass on a departing Air Canada, Air Canada Express, Air Canada rouge, Air Canada codeshare or any Star Alliance member airline flight.
Qualifying passengers are defined here:
http://www.aircanada.com/en/travelin...es/access.html
Presumably "Qualifying" passengers are the same as "eligible" passengers. Consistency is NOT AC's strong point when it comes to their legal work.
Also not clear from the AC's attempt at law here is what happens in certain situations:
- Standby (not confirmed) ticket holder?
- Booked on a flight that departs at 00:01 the subsequent day?
I'll say in both of these edge cases the MLL is generally "common sense" wrt to admittance, and I've never experienced any "dragons" as some post about here. All other circumstances are crystal clear to me.
Another useful tool is the Star Alliance lounge finder (
http://www.staralliance.com/en/web/s.../lounge-finder), in which you can literally enter in your hypothetical status, fare class, and route... and it'll tell you which lounges are supposed to let you in.