Here is a thread discussing your unit.
https://ogrforum.com/topic/operating-cattle-car
From the partial instruction sheet in one of the posts in the above thread, it would seem that wiring as shown in this partial instruction sheet would work as long as you common the transformer used with this accessory to the outer rail of the track by the accessory. I believe this is necessary because the accessory controller will supply power via the OTC to the pickup shoes of the Cattle Car, and the return path would be via Cattle Car wheels to outer rail, so for return to get to the transformer used to power the accessory, you must common this transformer to the outer rail.