I once spoke to a construction manager at comcast for their network buildouts. With my local township, they need to have 20 homes per linear mile along the route to justify a build.
Given it is Comcast, it appears that they are not interested. I know that some companies will do it if you pay for part of the construction.
Someone didn't do a very good job of negotiating their cable franchise. Around here (Tompkins County in upstate NY), the franchises with Time-Warner all say that they have to build on request anywhere there are 10 houses per mile, and at lower densities if residents will pay the difference. The local manager said they'd often do it even if it's not quite 10 because they don't want to lose customers to satellite, and I can imagine their pain when the 10th house is built, demands cable, and the other 9 already have DirecTV. R's, John