

I am pretty sure there is plenty of excess heat in the sewers of most cities. Compared to having to redo the street and sewers from salt damage, operate a fleet of plows and all the other currently used measures, it could even be worth it if the heat comes from a boiler.
less slippery than snow/ice. but to flash freeze hot spring water, that is maybe 50°C or hotter, it must be really really really cold.