AT&T has long history of this
If you've ever read the book Exploding the Phone by Phil Lapsley (a history of phone phreaks, the first hackers), this AT&T revelation is not a surprise. AT&T was so irritated by this community stealing free long distance they built their own Big Brother system to capture all phone traffic back in the 60s-70s. They used internally to work with FBI to track the phreaks down, especially the ones selling the black boxes to execute the hack. Once the FBI learned of it's existence, they buddied up with AT&T to go after bookies. Bookies, because of needing frequent long distance calling, were huge customers of the hack.
The most interesting part of book to me was how close Wozniak and Steve Jobs came to getting busted by FBI. They were making some money building and selling black boxes long before Apple was even a gleam in their eye.