Originally Posted by
jdtravels
The operator of the flight or the passenger's programme airline?

It seems to be a mix of both. Such as lounge access, it seems to be that operating airline pays based on class of service, and if you access a higher lounge based on status, the FFP pays.
eg
QF EMB flying JL J going to at CX F lounge, QF pays.
BA EMB flying CX F going to JL F lounge, CX pays.