Good Morning Hert
Due to the implementation of the new DLC system, existing 'installs' of the DLC packs in TS12 will not be functional in SP1. These packs must be downloaded and installed via the DLC system. When you first start Trainz, this will occur automatically.
If it does not occur automatically, then please click on the 'get content' option on the main menu, then click on the 'redownload all purchases' button at the bottom of the screen. You may wish to temporarily cancel some so you are only downloading one at a time, or you can simply let them all go whilst you play Trainz
Regards