This has also happened to me several times on BA at LHR T4 (...and LGW-N, and YVR, and YYZ, and JFK, &c &c &c). And I have also been on standby (for a LHR-ORD flight) there and passed through security to go airside. I also know from experience that in Canada, AC standby passengers are also let through security to go airside. Perhaps this would make life easier for gate agents if AC adopted this policy...
Also, those of us that flew CP know that they would usually not take stickers when checking-in for oversold flights.
[This message has been edited by Fly Boy (edited 03-12-2001).]