Going back to the question of price collusion, I have no doubt whatever that it operates here in Canberra. Almost all Canberra's service stations are Coles- or Woolworths-linked (Shell and Caltex respectively) and their prices are always identical. (They've been 149.9 cents/litre for months.)
Motorists are "represented" here by the NRMA, but the NRMA's price surveillance stops short at the NSW border....
There are a (very) few independent petrol outlets like United and 7/11. United's prices are lower, but unfortunately they're on the north side of the city and I'm on the south, so it's usually not worth my while to buy from them.
What it sums up to is that Coles and Woolworths have a stranglehold on the ACT's motoring public, act in collusion to set their fuel prices, and charge just to the point where they reckon they won't spark an ACCC enquiry.
Resale price maintenance is alive and well in the ACT.