I'm not 100% sure, but I don't think splicing the cable is necessary, you can capture broadcast packets and advertise as having a local ip address and capture the packets, whether in a LAN (a residence connected to the same router as the target.) or a WAN (Reading your neighbour's packets).

At least from a blue team perspective that's what I assume can happen. The power lines outside my home have the network cables all spliced together anyways, it's not like you'd have to make a new connection.