Comment # 3 on bug 973882 from Karl Cheng

An example of where Wine (In reply to Marcus Meissner from comment #1)
> in which tool are the wine based mimetypes prefered over the system ones?

At the very least Firefox does. If you download a text file and then click to
open it from within Firefox, it will open Wine Notepad instead.

Some Wine apps also take over the default file associations, though I don't
quite remember which ones (long since changed them).