So, there I was just today, trundling around the local training area.
On the FIA freq, I heard an IFR aircraft inbound to Bankstown from the west. Cloud was below MSA, so he was doing the RNAV into BK. He was still IMC; we were VMC, but any time soon he'd be dropping into our piece of sky. The sector controller gave us as unknown traffic to him. Pretty obvious who he was talking about, so I spoke up and assured ATC we'd stop manoeuvring and stay on heading till the other guy passed aft of us.
We never saw each other, but were unofficially separated by the helpful ATC and all went happily on their way.
I wonder how all that would have played out if I were on the proposed new system of 126.7 in G? Or, gods help us, on 121.5?
I'm not a fan of 20nm CTAFs out in the bush, and I hope that particular change doesn't get up. But to have aircraft on different frequencies in the same airspace is sheer insanity.