Can anyone definitively identify this thing?

That's the rare, and extremely elusive, Civil War era Optimus Prime.

It looks like they've connected it to your basic Milltronivich 9000c, in order to " blend in". It's mostly likely on it's way to Little Cybertron. Once it hits the black market, it will never see the light of day again.

 

Judging by the accompanying parts on the trailer in front of it, I would venture to guess that it's a boiler or industrial engine of some sort. It's made to run in the horizontal position based on the location of the controls; there are intake and exhaust manifolds; and the large shiny ring obviously fits into another part because it has been protected from the elements. It would be interesting to know, though, exactly WHAT the machine does.

 

I believe that is a pot hole filler machine ...

 

I was looking through comparable images of what it might be.
A trailered air / hydro - vacuum excavator thingy which avoids cables and pipelines and stores the excavated soil for off site disposal was the closest I came yesterday

- but looking again the trailer forms a part the unit as it has pneumatic legs on the frame.

It looks like the unit also has pneumatic legs high up (or else pipes attach to both) so it seems to pivot forward / towards you looking at the vertical sides of the trailer frame and that section becomes horizontal - though to me that wouldn't explain the control panel

If it was an hydro / vacuum excavator of some sort it would have a hose / piping extending when it was in working condition.

Maybe its being scrapped.

From here you're on your own

 

I meant to add it could equally be pouring something out rather than excavating.

With respect though to the OP's request for definitive answers : I'm sure it's a Dunkin Donuts machine for major events.

 

Grandma's house had a red dirt road going past it that the local road grader tended once a week, they did not have any potholes.

One of my fondest memories is sittin on the lawn watching it go by and tilling the dirt to the sides of the road, and then playing on the mounds after it passed.