Electric Powered Trailer - Airstream

It appears that this will not have its own battery(since they talk about making it lighter) and will rely on power from the tow vehicles in order to operate the electric engines. If this is the case, then it will not extend the range of a BEV since both the trailer and BEV are using the same power source to move the combined weight. It would, however, assist an ICE vehicle since it does not rely on battery power to travel down the the road and can also make enough energy to power these electric engines at the same time.