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.
Apologies for not fixing all the autocorrect typos...
“the Aussie PM was considering proscribing the organization formally.”
There was some kind of a terror raid by police yesterday, in Sydney. Related?
Good find. One mystery solved.