Just to totally throw a spanner in the works (and I have briefly scanned this thread, but could not find it mentioned - I may have missed it, if so, I am sorry).

Qantas have recently started providing what they call 'Business Lounges' at SYD, MEL, CBR and BNE domestic terminals - which are available to those flying in J, as well as OW EMD (but NOT OW SPH, which seems to contradict the OW rules). The Qantas Club is still available for OW SPH flying in economy.

Perhaps (and I am only surmising here, but would welcome comment) the contracts state that an airline is required to provide lounge access to OW SPH and EMD, as well as J & F paxs, where lounge facilities are provided.

Following on from that, where two levels of lounges are provided, the higher level is to be provided to EMD and F passengers (and QF chooses to extend this to domestic J [(since we don't have domestic F]).

There may or may not be provision for a third (higher) level of lounges.

So BA might possibly be complying with the letter (if not the spirit) of the contract by providing a lounge for J and SPH, another (higher and better) lounge for F and EMD, and a third lounge for BA F (if they deign to use it), which is not part of the OW contract.

Just a thought.

Dave