Is CATS the only musical they have given this treatment to? If not, what others?
No, there's been a couple of musicals (i.e. Broadway musicals) released on video. "Joseph and the Amazing Technicolor Dreamcoat" (based somewhat on Genesis 37-50 in The Bible. Pretty sure some liberties taken with Scripture here and there
Also, there's "Godspell" and "Jesus Christ Superstar" (again, definitely liberties taken with The Bible- but still enjoyable to see)
And of course, there's the 1966 musical "It's a Bird, It's a Plane, It's Superman"- which was aired in a TV adaptation once in 1975- and taped copies of this special now float around Ebay and the comic book conventions and such...