This is an interesting question, but one does not have a concrete answer without erring on the side of caution and simply saying no. Fireplace inserts are essentially pretty space heaters and experts on campers have differing opinions about the use of such heat sources inside of recreational vehicles. It may be that there are differing levels of electric capacity within the camper industry, and differing methods of obtaining that electricity as well.
It would be best to seek advice about this from your camper vendor about this. Fireplace inserts must be plugged into a standard, grounded outlet by itself, never an extension cord or surge protector. They draw 1400 watts, or 11.67 amps when the heater is running, similar to a space heater. Additionally, the vent should not be obstructed by bedding or other fire hazards, if space is a consideration.