Maybe the tank treads (theirs are steel, whereas ours have rubber track pads) break up the ice for the shovel bubbas. Of course, they may be using the exhaust to warm up as well...
Regards,
The shovel bubbas were probably transported by the trucks in the left of the image. So the tanks probably also help clear the road for the trucks. If cars or trucks are stuck on the road, just push them off the road with the tanks.