(NOTE: Comcast Call center rep on forums between calls/at home on forum. Not representing comcast in forums)

As I understand it, we have to send a "bootfile" to your modem that tells it how to work, we send it via a broadcast and only the modem with the right mac address will accept it.
That Bootfile will tell your modem what speeds its allowed and other specifics like ip's for the dhcp server and such.

I don't know how the bandwidth meter will be setup but hope people will be calm/civil about things till it becomes a issue that affects more people then are being affected now. (IE when 250 starts to feel like a small # in terms of bandwidth)