A little follow-up… it looks like the major deregulatory change was the Telecommunications Act of 1996; the “freeing of the phone jack” took place in the early 1980s or late 1970s, and modular connectors (RJ11) were widespread by 1985, so either that was a result of earlier, less sweeping deregulation or else it was simply an industry response to advances in technology.
A little follow-up… it looks like the major deregulatory change was the Telecommunications Act of 1996; the “freeing of the phone jack” took place in the early 1980s or late 1970s, and modular connectors (RJ11) were widespread by 1985, so either that was a result of earlier, less sweeping deregulation or else it was simply an industry response to advances in technology.