It's a beautiful picture, don't get me wrong! And I very well can be wrong about it. I just took a class on photoshop, so I tend to look for it more, I guess.
I have a couple of reasons as to why I think it is photoshopped though.
1. I have seen this exact picture with no fireworks in it. (and cropped I beleive)
2. The fireworks are in front of the castle, not behind and hte scale is really big. I don't know if they have fireworks over the lake or not, but these definately can't be wishes if they are falling in front of the castle and over the lake. (in my opinion)
3. The castles is very close to the train station and it seems too big for the spot it is in. Which leads me to think this is at least 3 pictures. One with fireworks put it, one of the train station and one with the castle brought in closer. The other picture I saw actually looks more photoshopped to me because it is bigger, and I swear I can see the connection points on parts of it.
Again I could be totally wrong. But the castle really seems to big for where it is at on the picture.
I do love the picture though!