Stevie, yes you SHOULD easily be able to obtain the GOVCO rebates, be they Fed or State.
How it's supposed to work is your bill is first paid for using the rebates, leaving your solar credits intact for you to reclaim when you ask, or periodically, whatever you have arranged.
In your case, if you NEVER get a bill, even in winter, you are supposed to be able to ask for a credit of any rebates, I'm not sure when, but if you have say a years' history of bill credits with your obviously efficient solar, you should be able to get the rebate refunded to you at some stage.
I'd be surprised, based on other thread replies here from AGL reps, if you can't get the rebates now, if you do have a solid solar credits history.
Await a rep from AGL to reply here, or search up a few of the many threads already posted here for a read.