It's not clear how the gameplay video has leaked, but it does confirm the identity of the buggie as the Wombat Typhoon, which Motorstorm fans will recognise as being the same buggy found in the original MotorStorm PS3 launch title.
It's nice to see DriveClub getting a bigger variety of vehicles, but the tracks aren't exactly equipped for buggies. They certainly look out of place racing on tarmac in the video. Really, there needs to be some off-road circuits to utilise them. Perhaps Evolution are gearing up to release a MotorStorm-themed DriveClub expansion?
Edit: More details have since come to light. Apparently the buggies will be part of a "Lunatics Expansion" pack that reprises some old favourites from the MotorStorm series. While it hasn't been formally announced yet, some images from a listing on the Hong Kong PlayStation Store have emerged detailing the expansion, so it seems likely that this will end up being April's update. Hopefully some new MotorStorm-esque mud tracks will be part of it.