said by Matt :

Additionally, the MSOs VoIP product never touches the internet.

said by funchords :

Except on Comcast, where it does -- albeit it never leaves Comcast's network but where it does ride on Comcast's network, that network is part of the Internet.

said by Matt :

Comcast controls the QoS on "their" network. Who cares if their network is attached to the internet or not, it never leaves their backbone so no, it never traverses the internet.