[!!!] FOR CHANGES/MODS/HACKS ON THE DEVICE I USE A UNIT OFF EBAY WHICH I (not a KabelBW customer!) NEVER CONNECT TO THE CABLE NETWORK FOR THIS EXPERIMENTS [!!!]
The Technicolor tc7200 runs linux. Neither Technicolor nor the cable provider (KabelBW) provides the sources for the GPL licenced code. Technicolor does not answer end-customer questions, KabelBW does not answer questions without a customer number (which I will not provide because it is not relevant for the request).
On top of that, the device is unstable and insecure (e.g. get admin password or do factory reset from LAN side with a single http requst) - yay! It is not possible to configure wireless (config page just shows up a error message), but wireless is still enabled.
To secure devices and network I had to add a second openwrt box and DMZ it (at least this works...).