mdmp stands for mini-dump, and contains machine-readable information about a crash. The txt file contains user-friendly information about the crash. You can open the minidump in an appropriate debugger to allow you to debug the game.
EA could use these files to try to figure problems with the game. Otherwise, these files are completely useless and can be deleted; they are just wasting space on your hard drive.
It makes sense to me now. The 26th is the day I installed the patch. Luckily my game never crashes, but that day it did because of a conflicting mod. Since the crashing no longer occurs, I'm off to delete the files. Thanks!
Not new... EA wrote minidumps for TS2 and now for TS3; I'm not sure about TS1. Unfortunately, without the source code, the minidumps can be pretty useless... they often only tell us that EA doesn't write very robust code.
CrazyAce, are you interested in specific crashes, or all crashes?