Everyone is put on the group date of joining list and you can bid for base and fleet changes, as well as command upgrades. So long as you are not under any freeze than you will be awarded the change if you have the seniority/DOJ.
What number is the lowest person on the group list now? And what number is the lowest Australian based 737/Ejet FO? Lots of 777 and VARA peeps in between and not a lot of growth likely for a very long time!!! You'll be in NZ for a very long time.