Buggyra is a private race team not a truck manufacturer.
They built their own racing special trucks like this specifically for racing.
They have since switched to racing "conventional" looking trucks using Freightliner cabs but the rest is Buggyra, engine, transmission, chassis etc. So the Fly model Buggyra is technically obsolete.
Technically neither Buggyra or Freightliner is listed manufacturer in European truck racing so I guess it would fall under Mercedes?
Sort of like this
They also modify cars
BTW I have a Fly Racer Buggyra and I knew they were a race team, the rest I found by surfing.