This possible class-action lawsuit isn't the real story here. Frankly, I doubt it gets a lot of traction. Instead, the real story came out earlier on MacRumors where it was reported the US Federal government was looking into the actions of MCX, RiteAid, and CVS.
I've had very extension antitrust training over the years and this prohibition of NFC payment options by the parties looks really bad on that front. Someone brought up the example that a merchant doesn't have to accept a credit card or even a specific credit card for a purchase. That's true. OTOH, a trade organization can't get into the business of creating uniform terms and conditions of sale for its members, which is essentially what MCX is trying to do here. It would be like MCX telling RiteAid and CVS that they may accept Visa but not MasterCard or even tell them they can't accept any 3rd party charge card. Yes, either RiteAid or CVS can make that decision on their own but they can't have an agreement between them to do so.
Here's the important part... the government doesn't have to present an ironclad proof of collusion. The appearance, means, and the result of collusion is sometimes enough to get a conviction. I'm reminded of this about once a year by my employer!