Never heard of DODX either, but considering the windows not being covered up, I'd say it's one of those fancy cabooses that sales people ride in when escorting some kinda large shipment on rails. Cabooses nowadays are either that or old, neglected ones that are used for switching and are boarded up.
Actually not all cabooses are boarded up..Some are still in service as fully operation cabooses.
This video was taken by a friend that lives in Marion.
YouTube - CSX local at Marion Diamonds
Another fully operational caboose
YouTube - CSX light engine movement
Have you noticed any all-black Suburbans with real DARK windows around since taking this shot ???