Couple of things: No TNM track Monahans to Big Spring. In Monahans the 2 roads shared a yard where traffic was interchanged. TNM track ran from Monahans to Lovington, NM with a short branch west to another town Wink, Tx
Yes the bad truck and train accident in Midland killing several people was on the main line of UP (T&P) in Midland itself just a few years ago and there may still some active lawsuits on it . I have always thought the 60 mph train speed limit was to high in city area with heavy traffic.
Yes there were some tracks south in Midland a long time ago and almost none today, but were all T&P. Odessa's track 's continue to expand and the yard was also enlarged recently.
There are many tracks in Odessa south of the main line and the refinery. In fact a map of them looks like spaghetti on a plate. At one time there were more than 100 switches off the main line in Odessa . There was a carbon black plant that put out a large and very dark smoke cloud that would do a steam engine justice. There were several carbon black plants in the area. But, here again there was not any steam running in Texas when FW&D finally retired its last steam engine in 1959 that had been only occasionally used as backup power. The last one I actually saw was a 2-8-0 in Childress Tx in 1957 switching in the yard. The last FW&D engine retired was a 4-6-2.
Good book in construction and abandonment with maps is " Texas Railroads, A record of construction and Abandonment" by Charles P Zlatkovich, a recognized expert on this topic. Bureau of Research, Univ. of Texas
There was an unusual steam engine on the T&P from 1958 to about 1962. It was a retired 2-8-2 of the FW&D #410 bought to put into service in Louisiana for flood duty. T&P picked it up in Ft Worth and pulled it to Marshall, Tx to a T&P shop and they got it running. The Red River would overflow and flood T&P's line south of Shreveport every spring and diesels could not go through water without shorting out traction motors. The 410 renumbered to 400, was classed as work equipment only, not a locomotive, although it was. But it never handled any train away from that area of flood water and of course never appeared in west Texas. It was kept in Marshall when not being used and today is a display at the Marshall station.
I am very familiar with the area around Midland-Odessa, and Monahans. Yes, T&P made many fortunes from the Permian basin on oil. And although now UP, it is still making a killing. TNM is now owned by a short line. All research I have done does not show another railroad running south from Odessa or Midland. If you find one, let me know.