Network connections over a powerline (CPL) are a flexible solution to extend the link for a digital decoder or a wired lan connection.
This solution will work equally to extend a wired ethernet connection between a pc and the Belgacom b-box and b-box2.
Here is a schema to extend your LAN over the in-house power circuit. In the example below, the LAN connection from the ADSL-modem is extended by using the Devolo MicroLink dLAN Ethernet adapters.
Be carefull with cheap powerline adapters, they may not be stable or may not support your (extended) in house power wiring.