The AT&T case basically said that once the implementations was released, AT&T could no longer call anything a trade secret, although they do the own the IP and copyright
Not entirely true. There was a preliminary ruling that said that 32V might have lost its copyright protections because it was distributed outside of AT&T without proper copyright notices, as required by the pre-1980 copyright law. This detail was what caused AT&T to settle before it could become finalized (the preliminary ruling said there was a substantial likelihood that this would be the outcome, to be pedantic). To the extent that AT&T had complied with copyright laws requirements, they would retain their copyrights though.
"Consequently, I find that Plaintiff has failed to demonstrate a likelihood that it can successfully defend its copyright in 32V. Plaintiff's claims of copyright violations are not a basis for injunctive relief."
being the appropriate quote. Plantif == USL.
Warner