When I heard about T gauge, along with ZZ gauge, on Wikipedia, it appeared that these were merely abortive attempts at a smaller gauge than Z.
However, I've come across a site, Tgauge.com, that is currently selling Eishindo T gauge trains. Eishindo itself has a site, but at least the English-language portion of it doesn't seem to be working properly - it doesn't load images.
Apparently, at least Europeans can buy T gauge trains.
John Savard