If Google and Apple were only participating to throw their around their weight as lobbyists to pass a new law -- similar to what Arkansas legislature tried to do, it might be a First Amendment debate.

However, a key sentence from the article was:

"concrete plans to accelerate the development and adoption of new tools and solutions,"

The "new tools" doesn't sound like crafting a law for a court to strike down but new technology to empower users to block the nuisance calls.