Not really at China Southern, but it was how CX did it back in the day. China Southern was reverse-scheduling port vs. CX's Australian base. Given Middle East promises are about as reliable as Philip Lowe's interest rate predictions, I'd be careful signing up for a reverse schedule by any of the ME3.
As far as tax, my understanding is that CSA pilots were still liable for Aus tax, but their salaries are net of Chinese tax. Therefore, with the Chinese-Australian tax treaty, you would give the ATO a certificate from China stating the tax paid and eliminate a double tax.
It would be good if the original poster would say which company called them. I know QR are losing crew to Riyadh with the 2on/2off deal, so my bet would be on them. I don't see EK doing it because everyone loves Dubai.
Anyway, it is all speculation, and I have no idea how it will be managed if and when it comes about.