ATT Advanced TV is another name for Uverse (on the commercials).
It utilizes a DSL signal to bring the cable into the home. From there it hits what is called a Residential Gateway (or modem) and from there goes into your cable boxes. (You need one box per tv that you'll want uverse on).
It does not always go through your existing coax, but it CAN; however each room DOES NEED a cable box, or the tv won't get the uverse.
There is no dish involved.
http://www.repaircable.com