My city actually signed Comcast into a legal monopoly to get them to bring service here in the 80s and 90s. That deal is still good, and states that they will be the sole provider of cable TV service at least until the end of this decade. From what I've seen, this was a common practice, and has apparently happened in a lot of smaller towns.
It happened a lot in smaller towns because without the carrot of the monopoly grant, it would've been undesirable for companies to wire up those little towns at all.
