Hi, so from personal experience owning for example almost everything that should layer and substitute on Leipzig-Dresden I never see any substitutions. Never see the 193 always the standard freight loco that comes with Leipzig-Dresden. Also from for example a recent Steam review of Stuttgart-Heilbronn "If you have all DLC except for the Semmering Railway, only BR 111 trains will be at Stuttgart Central Station at 12 noon. All freight trains I have seen are BR 140 trains with Hapag Lloyd containers." So similar experience as I have. Is this a know issue that AI layers and Substitutions are broken to some extend?
I've not got the game open at the minute - but I'm sure in TSW6 an option was added to the menu to allow substitutions or not... I've quickly opened it - make sure you enable substitutions -
This option is enabled of course. Since its enabled by default I don't think thats the problem when people complain about missing AI layers and substitutions