There is a product by Motorola called the Powerline MU. It is designed to provide MTU/MDU's (apartments) with high-speed broadband.
Basically, the 'access point' is installed at the meter bank. This lights the entire complex up on that meter bank. All of the electrical outlets on the meter bank there now have high-speed connectivity. Plug in your modem and you are set.
There are some catches on a system design such as quality/condition of the electrical systems interconnects (dirty breaker contacts, poor electrical wiring, bridge taps, etc) that can wreak havoc with such a system.
If you want to know more check out Motorola's website.