When you delete a file, the file will appear in the trashbox in a folder structure that imitates its original location. For example:
Delete a file in share/hop/scotch. => File is removed from share/hop/scotch, and will now exist in share/trashbox/hop/scotch.
Behind the scenes what happens on any hard drive when you delete a file is that the file's name, path, and list of reserved clusters are unlinked from the physical clusters in use. When that happens, the used space is essentially reclaimed and the file appears to be deleted, whether or not the physical file space has been overwritten.
So when it comes to the trashbox, it's not a stretch to conclude that the original file isn't rewritten, just that its filename and path information are altered so that it falls under the share/trashbox path instead of share/. But when that does happen, the original path is unlinked, and the file is essentially deleted.
I don't know if my explanation helps or not..... clear as mud right?