I believe the Michigan operation mentioned was called the Northwoods Railroad, as photos exist of the EBT cars lettered Northwoods. Hard to speculate what could have happened to the cars, but for now they still exist, are back at the EBT, and are stored inside.
Most wooden cars in Pennsylvania that were sold for use as sheds are on their last legs. Metal roofs allowed the cars to remain fairly watertight in our wet humid weather. Time is catching up, and cars grounded in the 1930's are close to collapse. Hiking in the woods to find such cars used to be a favorite pastime. Now its a hike to see the metal bones of the cars, trussrods, draft gear pockets, etc. EBT 18 and 29 could have easily met this fate.
brian b