I think those missing hops are the gateways, not the CMTS. There are multiple CMTS's in Anchorage for both cable modems and GCI's new Digital Local Phone Service (DLPS = VoIP without the internet), but even more gateways that lead to the distribution network. Because the return path back can come through any of the gateways via the individual's CMTS, it cannot report a proper IP address for the same hop. The gateways themselves are pingable - mine is 69.178.0.1, but since it's a single host and destination, there is only one path, and so it responds to ping.
It's an extra hop, but a necessary one. At least it doesn't add a ton of latency to the connection.