This change was made for Air Canada Aeroplan's top tier Super Elite, ie. you must be flying Air Canada or a Star Carrier.
There are exceptions. AC's CIC*108/16 says:
"Additionally, Star Alliance Gold members can access Star Alliance lounges when connecting to a Non-Star airline if a Star carrier does not provide air transportation to the customer's next destination."
I interpret this liberally as point to point service and not via a circuitous route. No Star Carrier serves ZRH-CDG non-stop but LH does serve it ZRH-FRA-CDG. In any case, the Star lounge in ZRH let me in with my Star Gold Super Elite card (not my LH FTL card) and didn't seem to be too concerned who I was flying with.
I have not had to argue the point of lounge access yet.
