At about 2:30 of this video you will see a brief sequence of Japanese three rail trains. This video was filmed at the Japan Model Railroad Association convention held this weekend in Tokyo. Out of maybe 1000 exhibits I would guess no more than 2-3 would O gauge 3 rail. The Japanese market is about 75-80% N gauge (either 1/150 or 1/160), 10-15% HO (usually 1/80) and the rest all the others.
I've come across one or two other 3 rail videos from Japan, but never found very much at all.