Access could be by status or by travel class. If you have both, but with different airlines, I am not sure which pays. However, I do know that the airline operating the lounge is paid a fee for each visit by the airline from whom the pax is getting access rights (if you see what I mean), that it is paid per lounge visited not per flight (so if a CX pax visits both BA and AA lounges at Heathrow then CX has to pay the full lounge access fee to both), and that the fee paid isn't standard across oneworld. I have heard rumours of fees as low as US$60 in some places but know (from a very reliable source) of one lounge that charges US$250. Hope that satisfies some of your curiosity...