Ozzie, it's really very simple. BA and QF fly direct between the UK and Australia and are the only airlines to do so. This means they share a monopoly. (Also, BA own 25% of QF). And yes, the authorities accept the situation.

Direct does not mean nonstop.

Other airlines are not allowed to fly direct between the UK and Australia but carry passengers between them via intermediate points.

Without being sidetracked about who does/does not fly between the UK and Australia, the point I made is relevant to the topic, LX not joining OneWorld (yet).

BA/QF have a monopoly of the direct UK-Oz route, but this doesn't seem to trouble BA within OW. BA/IB have a monopoly of the nonstop LHR-Spain market, again not a problem for BA within OW (and BA own 9% of IB). BA/AY have a monopoly of the nonstop UK-Finland market, but again this is not a problem for BA within OW.

Yet little LX, which does not share a monopoly with BA on the UK-Swiss market (and so far as I can tell does not compete with BA on routes other than between the UK and Switzerland), appears to present problems for BA within OW.

Mind you, LX's influence is growing. Three of the four baggage carousels at LHR T2 were disgorging baggage from LX flights on Monday!