I would assume that it boils down to whatever CB may suspect or have reason to suspect. If CB has reason to believe that there is collusion in setting common prices (which they would pretty much need a whistle blower to help them with) then they could investigate something. On the other hand, it could very well be that one carrier set surcharges at a certain level and others matched (although I'd find that hard to believe).

In the case of the *A partners that are also part of A++ it would make sense that the fuel surcharges are the same since they are part of a JV on all of their trans-atlantic traffic.