Thanks to chosenprime for posting videos of a ship parts shot on a blue screen:
Here is an interesting interpretation (if you don't like spoilers stop reading):
According to a guy who was passing by the set "Shia was jumping from the ship to a building" (thanks to ARIQ from TFW2005).
First it was believed to be a part from a ship. Now according to sigma1 (a member of Don Murphy's forum and a TF3 extra in Detroit):
"The shoot involving the train derailed is called "Mayor's Mile" and is a continuation of the Chicago sequence. The scene itself will take place in Chicago within the movie. It involves the intro of a main antagonist, (which is the large construct with 2 turbines in the rear photographed earlier when Detroit production arrived). I won't reveal just yet who it is, but he will then transform and reveal himself to be orchestrating much of the chaos on Earth, most Autobots arrive (Bumblebee, Ratchet, Sideswipe, Wheeljack, and the Ferrari) to battle him. Prime, Ironhide, and Josh Dummal are involved in another sub-plot that will be revealed later."
This points that these turbines are actually part of a Decepticon which I believe is Shockwave. Another interesting info that we get from this spoiler is that Wheeljack is the blue Mercedes (the Einstein bot).
Here is a closer look at the turbines shot a few weeks earlier:
Of course everything is just a rumor so take it with a grain of salt but still great possibilities here.