I have a propritary system called ZenseHome around in the house, all wall lightswitches and outlets are ZenseHome, and several ceiling outlets.
At some point, ZenseHome added MQTT support for their system, so I created this:
Pressing the Switch send a signal over 220V cable to the ZenseHome box, that post a message on a MQTT Tpoic, that Home Assistent picks up, and sends a toogle to the Hue Brige, that informs the Lamp over ZigBee..
Worked ok 
Later I introduced Node-RED: