As someone who did a lot of work in the early-mid 1990's helping to commercialize the Internet, I have to say that I must respectfully disagree.
AT&T, as they were constituted, had a very long history of secrecy and obstruction of technological innovations reaching the general marketplace. Let me ask you this, have you ever seem any non-Ma Bell publicly available books prior to the 90's describing how T circuits work? No, you haven't, because they didn't exist. This information was guarded very carefully by AT&T as proprietary information and as trade secrets. Very, very few people understood how these things worked back then, and most of those were former AT&T and Baby Bell employees.
Did Bell Labs create new things? Sure they did, just the same as Xerox's Palo Alto Research Center created things, and IBM's T.J. Watson Research Center created things. The difference was, AT&T had a government protected monopoly and used their monopoly power to stifle competition, so they kept all these things in-house. The other guys only dropped stuff that they didn't feel had commercial potential, and they weren't monopolies, anyway. It wouldn't have mattered if other companies came up with technological innovations in telecommunications, unless they thought they could sell them to AT&T, because they wouldn't have be able to commercialize them with AT&T controlling the market. The real advantage of the break up was not price competition, but that AT&T had to start sharing the market with other companies, and because of that, they were forced to let other companies know how to make their systems interoperable with the existing infrastructure.