You may not quite realize for how long roads are impassible to all traffic in northern states. Where I live, a couple hundred miles south of Grand Rapids, the snow and ice still make roads entirely impassible for a total of a week or so every winter; it takes the coordinated effort of hundreds of salt trucks and plows to get it cleaned out enough to drive, bus, walk, or bike on. Then that same effort has to be expended again a couple of weeks later.

Piping existing waste heat underground into a system like this, when the road is uncovered for repair anyway, would make a lot of sense for high-traffic areas so that plows can focus on other locations instead; it would also reduce the salt budget and plow fuel budget, and reduce the maintenance budget for cleanup and repair due to salt damage.

Going even a little bit further north, this would likely be even more effective. In some Michigan cities, roofed streets make economic sense; this seems even more cost-effective and less likely to require heavy repair.

Bike lanes, public transportation, roadway maintenance, and snow & ice clearing are all expensive. None of them have to turn a profit.