I have the new gameplay pack but the Metrolink holiday train and the BR 111 aren't appearing for me anywhere. I don't currently have San Bernardino or Frankfurt - Fulda, but the post here says: Just wondering if the post was mistaken, or if the gameplay packs are bugged --- Information has been updated to say San Bernardino is required
If you want to run the Metrolink holiday train and the BR 111, then you also need the routes. It certainly won't work without the tracks.
You can spawn them in timetable or sandbox mode, but to appear as driveable or AI in a timetable, you will need the route.
I could not spawn the BR111 or the holiday F125 in the timetable mode. They were also missing in livery and formation editors. HKAs worked as advertised.