DirecTV is piloting some Broadband over Power Lines in Metro. [engadget] Liberty Media, which now owns much of DTV, wants a broadband strategy. DTV had a DSL strategy that failed back in 2002. You would think satellite broadband, but not if they want HD content for DTV. (HD uses up more spectrum - sprectrum that could have been used for BB). [source] So maybe Liberty saw that the pilot in Michigan was working [GigaOm] and one in Arkansas, and Liberty thought, "What the heck. We got nothing else, cuz we can't afford AWS spectrum." Right now, BPL is 0.008% of the market.
As is described here, there are 2 types of BPL: in-house and access. This industry loves to use ambigous terms like wireless for cellular and BPL for HPNA. The FCC supports BPL access, since they like to keep up the chirade of "competition".