The police will only confirm one. I think his quote was: There is at least one.
bump
Australian News Network says the flag has been identified as that of Hizb it-Tarir.
http://www.hizb-australia.org/hizb-ut-tahrir/itemlist/category/11-about-us
Excerpt:
The work of Hizb ut-Tahrir is to carry the Islamic da’wah in order to change the situation of the corrupt society so that it is transformed into an Islamic society.
Found an article from Oct in which the Aussie PM was considering proscribing the organization formally.