MARC actually leased one or two Chessie GP40's for a long stretch, back in the late 80's early 90's as they went through their motive power crunches. At least one of the old F-units on MARC (IIRC, #9100) was actually just a cab car/HEP unit -- like a LIRR powerpack. For a long while this operated on the B&O side with a Chessie painted Geep from CSXT, so it was a regular fixture in Washington Union Station. Of course, this is back when MARC was a rolling railroad museum, with freight engines, ex-BN E-9's, RDC's, rebuilt F units -- along side a few AEM-7's for good measure!
Wondering if I'll see the Western Route double-tracking finished before I retire...
Photo: Melbourne W7 No. 1019 on Route 78, Bridge & Church Streets, Richmond, Victoria. 10/21/2010