This might seem redundant/stupid, but did CSX put anything in Marquette's lease that says they couldn't resume car ferry service in Ludington in order to interchange with whoever is on the other side of the lake and bypass CSX? I know it is far fetched and the infrastructure for shipping rail cars would have to be reinstalled in order for anything like this to happen but one thing that CSX always seems to be strict on maintaining is their grip on having everything for Marquette go via Wyoming.
1223 OUT! President and Founder of the Buck Creek Central, the Rolling River Route! (2012-2017) President and Founder of the Lamberton Valley Railroad, The Tin Plate Road! Proudly railfanning with Asperger's since 1996.
If I remember correctly from what I saw in the Surface Transportation Board filings the Marquette can interchange with railroads other than CSX but have to pay CSX a fee for each car interchanged with another railroad.
Marquette Rail can interchange with other railroads, but all of the traffic must go to CSX first. That is why the Marquette traffic that goes via the Grand Elk always has to go to Wyoming yard first.