I can't be definite sorry.
Direct entry should still be an option, it would be best to contact ASA recruitment and ask them though. There is no reason that they can't recruit you straight in as far as i know.
If you can get australian residency you can apply once here, no problem. I know of someone from overseas who got here first them applied for the job, and he is training at the moment....and he has no prioir ATC experience. If no one else pops up with more information i will speak to him when get back to work in a couple of days and ask him if there was any citizenship requirements to applying.