This hack is just a rip off out of the Codex tutorials, the FF method used in LL can also be used in rct2. First we make a track:
After that we put objects under it.
Now we search the tiles that have the objects on it: 
We take the first block of the object (the selected in this screen):
And we change this block to FF. We do this also on the other land tiles. After that we go back to rct2 and we see:
And you will see that trains still can travel over it:
The theory behind this hack is that by changing the first block of a object to FF it becomes deleted, normally it would be moved to the last place of the mapdata but because you edit it now it stays in front of the other things so all things behind it looks removed to but arent. . The only letdown of this hack is that you can build anything above this object anymore but there are ways to conquer this problem also. For example you can build the track first a lot higher and move the object up. Now use the FF method and after that lower the track by hex-editing or by using a alternate colorscheme. Now you are able to build objects on the same height as the track.