All the oil companies or servo's have to do is have thier "opposition" as a client, and notify them of impending fuel price changes by email.
From what I have been told is this is not collusion, and therefor not illegal.
Years ago, the companies would sit down with a beer, or over a game of golf, and discuss price tactics. That was collusion and made illegal.
I can't see the ACCC doing anything for what is a legal practice of notifying your client of price changes.
That is my understanding, and may be wrong, but I will defend my right to be wrong until Gillard makes that illegal.
Cheers