741st Railway Operating Battalion -- Harmon Lindsey

Jay writes ...My dad's older brother, Harmon Braxton Lindsey, was in the 741st Railway OPR BN TC(Not sure what any of these acronyms mean).
I also have a few pictures that are attached. If you have any information on my uncle, please let me know. He was KIA on 12/24/44 in Leige, Belgium. The 2 pictures where he is with his unit buddies, I have no idea who these men are or if they are even still alive.
One of them is from Chicago I believe and had a nickname. I also have a picture of my Uncle on a Train with his name on the locomotive.
 ** update May 2018 Jay writes .....my 86 yr old aunt whose brother was Harmon said the man standing in the picture with my uncle on the cobblestone street was named Mickey Dominic from Philadelphia PA. If you can post his name to that picture somehow that would be great in case he has Descendents still alive.