Is there such a thing as TSW2020? Jack, if you meant TS2020 then as Peter says they are in two different and incompatible games.
There was a TSW 2020 - which the BR 204 (Train Sim World®: DB BR 204 Loco Add-On on Steam (steampowered.com)) was released for originally, but I believe if you own it for that - you automatically get it for TSW 2 (Train Sim World® 2: DB BR 204 Loco Add-On on Steam (steampowered.com)) ? (but don't quote me on that )
If you mean the BR204 for TRAIN SIM WORLD 2020. Then yes, if you own it and the associated route in TRAIN SIM WORLD 2020 you'll also have it in TRAIN SIM WORLD 2. If you mean the BR204 from TRAIN SIMULATOR 2020, then no, you won't have it in TRAIN SIM WORLD 2. They are different games build on different engines and in no way related other than both being developed by Dovetail Games.