Lets assume they are using the +20MHz spectrum. There are a few installations in the US (I believe one is in Colorado). Essentially, a collector is installed on the LV side of a power line transformer. (The transformer acts like a filter to the signal, isolating the connection from other neighborhoods.) This collector is typically connected to another technology as the backhaul. In Europe, it is reasonable to expect 200 homes on a single transformer, so it is very cost-effective for this kind of utilization. In the US, you get only 1-8 homes per transformer, so the cost is fairly large. If you really need to, you can use the MV line to transmit this PLC as a backhaul.
200Mbps is the Maximum amount, used for marketing purposes. In Europe, they can have a couple hundred houses connected to the same LV transformer. This means that you are sharing a 200 Mbps connection with the neighborhood. If you assume 100 homes for one transformer and 50% utilization, a home can get a maximum of 2Mbps (assuming an ideal backhaul). As you all know, this is an "ideal" number. If they try to use PLC as the backhaul (instead of fiber), then you share the bandwidth with other neighborhoods, reducing your datarate well below 1Mbps.
Other considerations: Repeaters.
Underground wiring is another filter. This kind of technology will require a repeater every 100 meters for a full underground installation. Overhead wires need a repeater every 500 meters or so. If you are in a high-noise environment (as in, there is a factory connected to your substation), datarates are decreased and more repeaters are required.
Simply put, the final system will look closer to 500Kbps per home and it will cost a significant amount of money to the homeowner, either through taxes or through required rate hikes on your utility bill.)
So if you want to use PLC to help solve the ISP monopoly, you are looking in the wrong place.
Signed,
A Smart-Grid researcher and designer for the US market