The devices are set top boxes, modems and more. Those devices only have a single plug that plugs them into the network, technically it is all inband.
It's only separated in that your cable modem gets a non-routable IPv6 address. It's non-routable within the internet but is a stock standard globally unique IP address. This is used for management purposes.
From: http://meetings.ripe.net/ripe-54/presentations/IPv6_manageme...
In the control plane, all devices need to be remotely managed, so NAT isn’t going to help us, nor is federated Net 10 islands…
IPv6 is the clear solution for us.