Well, yes, after two or three years of neglect, they are certainly in need of maintenance. And a “TÜV” certification is required in Germany, for safety of operation.
However, as I mentioned, the engineers and technicians at Europa-Park are very experienced in such things. They also partially rebuilt two of their trains that were damaged by an accident a few years ago (thankfully there were no bad injuries, only the train driver and another employee were slightly injured). Here’s a short press coverage:
(Sorry, it’s in German, but you can clearly see what happened. Basically she says that the passengers were rescued by the park’s fire brigade, and that the cause of the accident and the damage sum are yet unknown.) The track and trains of the EP Express are equipped with proximity sensors and block control, that should normally prevent two trains from coming too close to each other. Operation of EP Express resumed the same afternoon, using the third train. One of the damaged trains was repaired and back in operation the next day already (it only had some body damage), the other one took somewhat longer because the control panel in the driver’s cabin was affected.
It’s also interesting to know that the trains at Europa-Park were somewhat modified. In particular, they got air condition back in 1995 (that’s the bumps that you can see on the roof of the trains). As far as I know, the trains in Australia did not have air condition.