Ted
I’m not surprised you haven’t found any information. Mopac customer and agent pools were retained in TCS and there was no reason to print out and save hardcopies of assignments. Cars before computerized pools assignments, (which drove the empty waybills back to the origin loading point) had customer or agent stenciling but these were painted out once the TCS pools were implemented to avoid any confusion. Your correct about the offline pools where MP shared in the roadhaul. They would participate in the foreign RR pools by assigning cars.

Charlie