It must be an International thing with Fire vehicle driver training, and reversing with mirrors!.
Given that you can't see through the back window of most Fire Appliances.
I never look over my shoulder when reversing, I haven't in years, but you are right, it IS a hard habit to break.
Another thing that really annoys me about drivers over here, is thier inability to reverse a car with a trailer connected to it, without getting the thing all twisted up.
You should see the local Refuse Dump on a Saturday afternoon, it's like watching a pit full of snakes!.