From what I remember is they had what I think they were generators built on trailers, trucks that came and went and road cutting saws. There were several of each of these distributed the full length of the bridge on both sides. They took up a lot of the 2 outside lanes in both direction, where they were working.
This is kind of vague, but hopefully it is helpful.
I would think that the truck mounted items you saw were truck mounted air-compressors as opposed to generators.
Compressed air generators and the trucks are not heavy virbration or dead load.
Compressed air is used to blow off the light debris and dust after the larger chips are removed behind any scafication operation. That gives a clean surface that the topping / resurfacing can bond to as it is placed.