Cheryl,
You might not hear back for months. They are in the middle of an overseas hire right now. I'm not sure they are even taking applicants anymore. If you look on their website it says what they are hiring for and taking applications for. First trainging class starts tomorrow (with myself, a guy from the UK who is going to Sydney and purpleairspace)
My timeline was:
ASA emailed me in Feb asking if I wanted to apply for the Sydney job
Offer came at the end of July
Start Tomorrow
The process has been pretty time consuming. I am from the US and have moved over here and will be getting my residency, so no you do not have to be a Citizen of Australia.