I've seen one or two homes that had wall switches without any line voltage in them. I'm not sure what history would lead to someone having a rack of relays in the basement utility room sending power to ceiling lamps.
One set of switches I recall involved something more practical, and that's why I'm posting this. These switches were controlling lights in and around a swimming pool, but with all the power coming from the pump room in the pool cabana. I remember these switches weren't controlling relays, but were closing a secondary circuit in some sort of transformer arrangement that I can't recall. I'm pretty sure the closed switch in the secondary circuit made for an increased magnetic field that was used to close contacts, so the function was like a relay, only there was no specific coil with a voltage rating needed to operate it.
Any of this ring a bell? I rather liked the simplicity of the concept. I saw a data sheet for these low-voltage (or nearly "no-voltage") switching devices, but I just can't remember enough to locate them again.