Originally Posted by House
I would also guess that different solutions will be used at different times of day, but the bottom line is that if AS can give you your BA boarding pass, then you do not need to exit all the way to the check in hall.
Greetings from the BA Arrivals Lounge at LHR T4.
Thought I would follow up on what happened on my trip.
1. AS did check the luggage through PHX-SEA-YVR-LHR, but could not issue a boarding pass for BA.
2. The immigration at YVR did not have the full transfer desk open, but they did direct transfers to the far right window-- outside of the big snaking queue.
3. Immigration officer checked that the luggage was tagged through, gave back a Pink card and sent me back along the wall to the elevators (underneath and behind the escalators that bring down the arriving passengers).
4. Found (after some wandering) the BA lounge and checked in.
All in all, very convenient. Perhaps would be less so for anyone unable to use the lounge to check in-- I suppose you'd have to do it at the gate.