Got it in one.
Its used to clean underground pipes by pumping ice under pressure to scour the inside of the pipes. Shifts all the muck and debris etc. The unit at the front generates the power for the refrigeration unit and the tank holds water which freezes into slush.
The model was built as a personal build but the company persuaded me to part with it.
Trailer wheels and suspension from Kfs, Premium kit courtesy of Mixxy, everything else more or less scratchbuilt.