The locomotives are EMD RS1325's, which look like an SW1200 on flexicoil trucks with the low nose and cab from a GP18 replacing the regular cab. It was basically an EMD version of the GMD1 and was in the catalog for a while but sold only to C&IM.
Here's the link to some photos of them: http://www.railpictures.net/showphotos.php?locomotive=EMD%20RS1325