So long as the tanks are within the insulated camper, the camper is heated, and you have adequate airflow between the living space and the tanks, no worries.
We have seen well below zero for weeks at a time, without any freezing issues in our custom hardside.
No black tank, but fresh and grey are both within the insulated camper.
For serious cold, electric heating is not the answer.
Gas rig, or on a budget, go propane.
Diesel truck with a good budget, look to diesel appliances, including furnace.