The 2011 Australian Book Industry Award for Older Children went to...
...365 Conspiracy, by Gabrielle Lord.
I'm not sure if that means to the series as a whole—it was released in twelve parts over the course of a year—or one specific installment.
Also of note (to me!) was the Biography award, which had co-winners this year: Anh Do, for The Happiest Refugee, and Paul Kelly, for How to Make Gravy.
And we all know how much I love Paul Kelly.
The rest of the list is available through the APA website.