I would submit that you are making a common mistake in applying an engineer's or programmer's mindset to the law.
What I am thinking of is that company that tried to get around copyright by having their customer's buy TV antennas located at their HQs and then they would stream the feed from the antenna to the customer. Every piece was technically legal but because the entire scheme resembled a patently illegal activity (profiting from distributing copies of copyrighted material) the courts shut them down.
Similar reasoning will be applied in this case. If enough of the market is using the same service to set prices, that will be struck down as collusion.
What I am thinking of is that company that tried to get around copyright by having their customer's buy TV antennas located at their HQs and then they would stream the feed from the antenna to the customer. Every piece was technically legal but because the entire scheme resembled a patently illegal activity (profiting from distributing copies of copyrighted material) the courts shut them down.
Similar reasoning will be applied in this case. If enough of the market is using the same service to set prices, that will be struck down as collusion.
(All IMHO and IANAL)