Recently I've seen a lot of large government trucks going up and down I-25, mostly north of Denver. They are GMC or Chevrolet 5500 4 door cabs, 4x4, with a large box on the back with a spare tire flush mounted into the back. There are no windows on the box that I could see and have double doors on the rear with a step. They have flush mounted LED lights, which I assume to be emergency colored as they weren't on, just a clear lenses aroudn the perimeter. Some trucks dark blue, dark tan, and a few have been black. All of the cabs have dark tinted windows and the driver's all appear to be government "operator" types with ball caps and goatees. The trucks usually travel in groups of 3-5, with smaller dark blue F-350 4 door trucks with fiberglass modules working in the vicinity as well. All the vehicles have quite a few antennas and just plain government plates. No markings or designation on the trucks. Anyone seen these?