It seems as though when replacing an existing object with a new one, when the original object is close to a tile boundary, TSRE wants to place the new object on the adjacent tile instead of the tile on which the original object was located.
Case in point:
Here I am replacing the stock grade crossing signals on this route with new objects from Travis Ebner's crossing package. Here's the original crossing signal before deletion:

Number of downloads: 3
Make note of the tile X and Z ID's, as they will illustrate this problem.
Now, look what happens when I place a new crossing signal at that exact same intersection:

Number of downloads: 2
You can see that TSRE has placed the crossing signal at tile X -12160 instead of -12159 like where the original signal was. Normally, this is not of a concern for static objects, as I can easily place the new object somewhere else on the "correct" tile and copy the Pos/Rot of the original, but with "interactive" objects that are "anchored" to the track and/or road, this can cause some problems.
Just thought you guys ought to know...