My guide on citizenship covered this. But please use this only as a basic reference, the processes might differ (some processes might have been removed, added or modified).
At the time of writing this post, the "official" processing time is 12 months. In reality, however - It ranges anywhere between 6 months to Forever. A sizable portion of the applications are processed between 6 - 9 months time.
Though we send the initial application to CPC - Sydney, further processing of your application is generally done by the office responsible for the location you live in.
The basic consensus of how a citizenship application might progress is explained below. This might vary slightly between applicants but this should give you a general idea. There is some speculation here and I am paraphrasing this from one of dpenabill's post and other posts in this forum.
CPC-Sydney issues an AOR after the completeness-checking the application package
My guide on citizenship covered this. But please use this only as a basic reference, the processes might differ (some processes might have been removed, added or modified).