When I pulled my tranny, I seem to remember the top two bolts being 12-point, but it's probably been over a year at this point. Maybe they were an actual reverse Torx, I just used a 12-point socket.
In my experience, OEM's generally put strange fasteners on things they don't want Uncle Bob monkeying with for whatever reason. Snap On actually makes a socket that fits fasteners that LOOK like internal Torx fasteners, but it has 5 points instead of 6. They'll also only sell this thing to "qualified technicians" probably because the most common use for it is servicing the injection pumps on diesel engines made by numerous manufacturers...