detroit & mackinac
Of all the Michigan lines I have chosen to model, the Detroit & Mackinac is the only one that did not directly interchange with the Ann Arbor. However, if you review any of the car lists or train orders from the Ann Arbor, you will find numerous references to D&M hoppers transported over the line, hauling stone, coal, sand, cement, and various other commodities.
It is also interesting to note that after the Ann Arbor car ferries shut down in 1982, the Michigan Northern Railroad took over the operations and added the Ann Arbor route and equipment to its service area: which included Cadillac to Mackinaw City. As the Ann Arbor's GP35s were more dependable than the Michigan Northern's fleet of GP7s, Ann Arbor equipment was indeed dispatched to Mackinaw City, and there exists a photo of AA GP35s and the AA snow plow under the I-75 bridge in Mackinaw City, with the Mackinac Bridge in the background.
So in the spirit of AA power in Mackinac, I just had to model some Detroit & Mackinac equipment! Links are included below:
Detroit & Mackinac Alco C-420 #976 crosses a stream on the author's layout