Besides what you have already for TAILCHASER'S SONG, I have:
Italian: Il Canto di Acchiappacoda
(1986, A Mondadori; ISBN 8804291419; Translated into Italian by Papi M.)
Russian: Хвосттрубой, или Приключения Молодого Кота
(2004, Азбука; ISBN 5352009378; translates to roughly "Hvosttruboy or Adventure young cat")
Japanese: テイルチェイサーの歌 (文庫)
(01/1990 出版社: 早川書房 (Hayakawa Publishing, Inc.); ISBN 9784150201340; Hidesato (translation))
Not sure if there are any others out there; these are from the research I did several years ago. The languages I found for any of Tad's books included: English (US & UK), German, Dutch, French, Spanish, Italian, Swedish, Finnish, Danish, Polish, Czech, Croatian, Bulgarian, Russian, and Japanese.
But that's only 15 languages, and there should be more -- or so I've heard. I've /still/ never had a definite answer about how many languages Tad's books have been translated into. (Even Tad and Deb don't seem to have that answer to hand.) Someday, I'll nail it down, though.