"Another noteworthy step taken by the commission [ICC], was the provision in Service Order No 71, issued March 6, 1942, that when any station or terminal was served by more than one railroad, all livestock cars were to be pooled. Pursuant to this, pools of livestock cars were established at St. Joseph, Kansas City, and St. Louis, Missouri; Wichita and Atchison, Kansas; Omaha, Nebraska; Sioux City, Iowa; Pine Bluff and Texarkana, Arkansas; Pueblo and Denver, Colorado; Fort Worth and Houston, Texs; Oklahoma City, Oklahoma; and Ogden and Salt Lake City; Utah."
Based on interviews with Car Distributors I worked with, these locations had livestock "reloading", both resting, feed lot and resales, besides the associated meat packing. As such, during WWII it was easier, quicker and faster for the serving carriers to utilize each others cars instead of going to the effort to reswitch, clean and prep the cars and respot. Mixing of equipment regardless of destination was commonplace.
I cannot answer if it reached "East" of Chicago.