A lot of cars were assigned to pools managed by other railroads, for industries on that railroad. As an example, there were MP RBL’s in Southern’s pool for the Stroh’s brewery in Atlanta. I would imagine there were some MP cars in the pool for Miller’s facility in Milwaukee. MP cars would be in any pool for a Miller plant where MP participated in the routing of outbound traffic. I have dug around and not found any specific info on the assignments for ARMH RBL’s, but I continue to search.

As an aside – the AB brewery in Houston was served by MP. It was located on the Houston-North Shore route to Baytown, and served out of MK Yard.