Look at the bottom of the steam page where it shows Downloads notice yours shows manage. Everytime somethings is updated it downloads and installs the fix. And at the bottom the word manage is swapped with 1 of 1 items Complete. If move the mouse cursor over the library tab, then click on downloads you should find that it downloaded something for TSW. There was patch put out today as nothing shows in there. What you are pointing to on the steam page is the icon showing that the Class 31 is available for TSW and not the update.
Sorry guys, a bit of a miscommunication on our side. The update will go out across all platforms around 12 noon (UTC) today. Best, Steve
It's a mod, which you can find here: http://www.trainsim.cz/?mod=article&nod1=33&nod2=2 And a thread to discuss here: https://forums.dovetailgames.com/threads/loco-substitution-via-mods.19139/