This was posted on another forum by the person who contacted the RBA,as sellittobuythat posted.

I received a call back this morning from the lady I spoke to (at the RBA) the other day about the release of 2012 banknotes into circulation.

She mentioned that the notes that have been released are $5, $10 & $50. These have been released to "any" areas that required additional notes. So what she said is that because on ATM's give out $20 or more, it's likely that you may strike a chance of getting a 2012 $50. As for the $5's & $10's you'd be much more likely to receive these from a bank counter or from retail traders (who have got those denominations as change from a bank branch).

There's been a couple posts already regarding these notes either being found or being sold on eBay.