Fog diverts in Australia


It seems like the annual September (late winter/early Spring) fog diverts have started in Australia. Sydney is not accepting arrivals this AM, most international flights being diverted to Brisbane. I have a friend on a United flight LAX to SYD that was diverted to Brisbane this AM. They are sitting on the tarmac now and not allowed to deplane. Apparently a big issue at Brisbane is that United has no personnel there, and when United flights are diverted there, the crews are already very close to being illegal. If the crew becomes illegal in Brisbane, a United crew will have to be brought up from SYD or MEL.
Has anyone else experienced fog diverts on long international flights and willing to offer any insights?