JTPorkins

You can just cut them out and replace them with Ethernet wall jacks, they are pretty cheap. Most have color coded punch downs on the back. Use the existing phone lines to pull the cables through the walls to wherever the phone lines end in a junction and that's where you can set up a switch or router.

This is covered pretty well in the Discworld series with the druids.

PTSD flashbacks to Anor Londo...