MarkoH01: The game does not list them as being there when I am offline - even though they are already downloaded.
Nice catch !! I didn't noticed that !!
But I just tried to launch the game offline, and even if it doesn't list those DLCs in the "What's new" section, I actually have the additional content in my stash ("Badland's rider outfit, Masquerade outifts, etc..."), and I can use them.
I don't have time now to check the state of the additional missions, but I suppose them are there too, I see nothing wrong in my quest log, else this thing could break a savegame...
Maybe the "What's new" list is taken from "your" profile in techlan servers, when online. (This is only a supposition, because the original game needs a user-login, while with galaxy it's not required, so maybe the profile is automatically created)
EDIT:
Anyway, a thing that I never tried, is to backup the files listed some posts above, and put them in a vanilla offline installation, to see if the game starts with the missing DLCs without even the need for a single connection.
A confirmation on this could be very useful.