I encountered many non-fitting substituted locos on the German freight services in the scenario planner. Even locos like the 146.2 which is passenger only and the 143 which isn't powerful enough for most of the services. In scenario planner you already choose which loco you want to appear on the trains so substitution doesn't make much sense there in my opinion. It even happens on the train you want to play so if you for example choose the 155 you get a substituted 143 or 185.2 even though you wanted to play the 155.
