Further information re Australia.. you do need to eligable for permanent residency as already mentioned. You will also need to do some conversion exams for your ATPL, as well as flight tests for any flight quals/ratings you may have such as CPL/ME/IR and get a CASA class 1 medical.
I have been looking at the option also. If you use the below link it will take you to the CASA website and give you all the relevant info you should need for flying in Oz.
http://www.casa.gov.au/pilots/index.htm
Good luck.