Ahh. This would've been for any eagle eyed spotters.
Between ride opening and the final theming elements, they had a "merlin studios" van on the mud behind the queueline and station - could clearly see it from the lifthill if you looked left. However, as you looked on top of the truck, it was just a repainted YourDay van from towers. The top still had all the advertising and logos.
Highlight of lifthill experience.