You're using a very old InDesign workflow which I've never used. But it's referenced in Olav Kvern's and David Blatner's excellent "Real World InDesign" (I'm looking at the CS4 edition).
On page 235, it reads, "The first characters in a tagged text file must state the character encoding (ASCII, ANSI, UNICODE, BIG5, or SJIS), followed by the platform (MAC or WIN). So the typical Windows tagged text begins with <ASCII-WIN> , and the Macintosh version begins with <ASCII-MAC> ."
It looks to me like it should work. Have you tried exporting some tagged text from InDesign to see how it looks? File > Export > Adobe InDesign Tagged Text.
I copied your text from your post, pasted in a text editor, saved. Then imported into Indesign with "Show Import Options" and then turned off "Remove Text Formatting" and file imported fine [without tags] and the text formatted the way it was suppose to be.
Here http://indesignsecrets.com/forum/general-indesign-topics/adobe-indesign-tagged-text-files is one of my answers on the same issue from InDesignSecrets, whcih self-referentially points you back at a few discussions in this same forum.
I think the basic idea was ID doesn't like a Tagged Text file marked as Mac to have Windows' line endings, and the reverse.