Yes - for the lounges and arrangements that I'm familiar with - my info comes from the senior airline execs themselves.

Now - that doesn't mean that other airlines and lounges within OW have different arrangements.

It also doesn't mean that there aren't differences between standard lounge access (such as Admirals Club or Business Lounge) vs premium lounge access (such as Flagship Lounge or First Lounge).

Also - getting off the oneworld-specific discussion....

Often it is actually the marketing carrier (as opposed to operating carrier) that pays for lounge access.

Additionally - many airline partnership agreements are assumed 'traffic-neutral', in which case - in many instances there is no transfer payment for benefits/lounge access. This varies depending on traffic imbalances and risk-aversion for the particular carrier.

So the short answer - is that like many things - "it depends".