I am a new Smart owner too. Purchased a 2008 451 with 25,000 miles on it here in San Diego.
Mine had the Blue Ox Base Plate and Alpha Towbar. I just took it all off yesterday as I won't be towing it anywhere.
I did notice that while uninstalling the Baseplate it was mounted by 2 large bolts on each side just behind the metal bumper crash bar (where the airbag sensors are mounted on the back of).
Not sure if that helps but enjoy your Smart. If you have any friends that want a Blue Ox set-up for $750, lmk!