An image posted on the Michael Bay Forums has added more confusion to the issue of what Transformer the Rosenbauer Panther airline fire truck seen in Chicago is. Set rumors and a toy listing indicated the character is Sentinel Prime but the image of a redacted call sheet now adds Ultra Magnus as a convincing candidate. It could even be one or both of these characters are pure CGI creations much like most of the Decepticons. As always, only time will tell. Thanks to Sam for the link.
Update: From Max in the comments, another call sheet image that once again references Ultra Magnus where it says "VFX:" near the bottom.