You know, in the real world, I don't think it does, unless you've got a really old building with rotting wires.

What I'm guessing here is that the ice cube cooled off the thermostat so it would turn the heat on, and then the water from the melting ice came in contact with the electrical wires and shorted them, causing sparks that ignited the isopropyl alcohol that had been poured around the place. Ingenious! -- but I'm not sure it would work in the real world. For one thing, most thermostats nowadays have their heat sensors somewhere other than inside the thermostat itself. They're also connected with insulated wires so a little water won't short them out that easily. I suppose, however, that this being the Old Town Hall, the wiring might have lost its insulation and just be naked wire. In which case, the building was a time bomb anyway, and it's just as well it's being demolished, right?

On the other hand, I would CERTAINLY not try this at home to find out.