This quote was taken from the official DIMA site:
Q. I have just been granted a migrant visa - am I entitled to any additional baggage allowance when I migrate to Australia?
A. Some airlines may offer additional baggage allowance to persons who are migrating to Australia for the first time. DIMA cannot advise you on additional baggage requirements. You should contact your travel agent or chosen airline to check your baggage allowance and what "conditions" apply. For example, if you are the holder of a temporary provisional partner visa (subclass 300/309/310), you may not be entitled to any baggage concessions. Holders of permanent visas should contact the International Organisation for Migration for information on reduced airfares and baggage concessions.
I have also read that Qantas, Singapore and Air NZ, do allow extra baggage allowance in some circmstances, but you would need to ask your chosen airline, so as to be sure not to get hit by excess baggage charges.