Yes, but we understand that game and have a strong legal base to tackle it as well (see: Cartels & the Sherman Act/Clayton Acts).
Further - It's REALLY hard to keep a cartel stable (much less secret) if there are more than single-digit members. Hell - OPEC is a great example. It's only 12 country members, and they can barely hold the thing together. Angola just left last year over disagreements...
So breaking up the monopoly and continuing to apply existing cartel laws would be a perfectly fine approach to tackling this problem. It's really disingenuous to imply we can't fix this. We can and have. It's like people don't remember "Robber baron" history at all...
Game theoretically, these groups would still collude to maximise profits.