Epiphany, as I understand it, KRudds recent change to 23AG has no effect on people working in a tax free country. Before the change they should have been declaring their full income and paying tax in Oz, unless they had non-residency tax status. (should have being the operative).
Working in a place like Nigeria is another story. Tax is paid on your behalf and there is no dual tax agreement with Oz so the money was effectively tax free. Not anymore. That conbined with the strong and strengthening ozzie battler will take a huge gouge out of the take home pay of the convicts.