Cisco and Charter internet have it done
It is NOT IPv6, it is double NATed IPv4 and then carrier grade nat as it exits the charter network in Detroit. Each static subnet cable modem has 2 paths, one paths is the static address pool and the other goes out the double NATed carrier network. Prolly using Cisco FabricPath
If Cisco was smart they would come out with IPv7 that fixes all the complexity of IPv6 but allows the use of IPv4. Dual stack OSes suck, remember Windows NT - IP and Netware - NCP?