In a truly free market, companies aren't supposed to do anything and are more than free enough to coordinate at any level they want if it is beneficial to them with the only checks on coordination and all being game theory situations about the value of the profits that come from breaking away from and undercutting the cartel versus the ensuing loss of profits from the price war or from "punishment" by other cartel members. In a regulated market though, sure, companies aren't supposed to coordinate at that level in ways that violate the law, but this doesn't violate the law.