Well, there might be, but I'm pretty sure I remember reading that you need Linux when this stuff was released, and I don't think that's changed. Then again, most of the stuff installed by that toolchain build script seems to be available through cygwin, so possibly it could be done that way. But I couldn't say for sure.
EDIT: Oh wait, the script builds custom versions of those tools. Perhaps these could be done for Windows, perhaps not. Dunno really. BTW, there is a discussion group about developing for MINI:
http://groups.google...mii-devel?pli=1 but it doesn't seem too active. Try asking in #wiidev on EFNET.