We got the lights up and running this morning. Switch is fine, and looks to have been recently replaced. When the switch is flipped, it kicks off the breaker and kills nearby circuits. Oddly, it trips 2 different breakers at the same time.
Izzy will have an electrician track down the trouble when possible.
We were unable to find what the switch operates, but we didn't check outlets. It does not appear to be a light.