I'd be shocked if they weren't. But the Feds like it when private suits do the heavy lifting first, and they cruise in and take a quick victory. Civil plaintiffs have broad discovery powers (pretty much going to be able to read all the important insiders emails about the company) that the Feds lack.

Shouldn't CMS be doing that?

The article mentions CMS threatening to revoke their license, it seems like they would be inviting in a law enforcement investigation if they felt it was warranted.

Unfortunately, it seems unlikely there's a public and open tip-line for general corporate malfeasance (that anyone's paying attention to anyhow).

Fortunately, I think the feds are already on the case.