found this on another thread,
You have to inform DIAC of your new passport details. You don't have to go in person, just fill out form 929 http://www.immi.gov.au/allforms/pdf/929.pdf and send it by snail mail or fax with a certified copy of the new passport (don't think you have to certify it if you fax, a colour scan is fine). Once DIAC has these details, they will transfer the e-visas over to the new passports. This, plus a copy of the grant letter is all you generally need to travel with. Whether you choose to then go to the office at some point to get a paper sticker put into the passport is up to you