Re: taken steps to shut down the Beeper party and indicated that it would continue to do so
They have arguments for why it's not. The two components are the following:
The method used was breaking security measures quite a lot. It allowed any person, unauthenticated, to send a message into the iMessage network. The iMessage network is supposed to verify the sender so that you can't spoof the source of a message, and this bug allowed anyone to spoof. Thus, their patching it was to fix that problem. If they need to, and for the second reason I'm not sure they do, to pretend that they didn't do this to break other services, they have that legitimate security problem to explain the need to prevent the method from working.
The other reason they have is that they can claim that they already interoperate by having SMS, iMessage, and eventually RCS in one application that automatically manages it all. Therefore, if you can use iMessage or not, the only difference is the color of the bubble. The message will still arrive to the same place for any user. Any user can still message any phone number from that app. Therefore, they can claim that their application is already interoperable. They can also claim that they have no need to provide services to people who chose not to enter any agreement or purchase any product from them, so denying service to Android users is not anticompetitive any more than not keeping around Safari for Windows was anticompetitive. This argument is easier to debate, but it still requires us to define exactly what market they're restricting competition in and what responsibilities they have in that market. Restricting competition by breaking things is often an easier case than restricting it by not providing things, so it's not going to be an open and shut case.