That's really interesting. I found Mirror B's tunes to be some of the best in the series along with the Goldenrod City, Ecruteak City and Gold and Silver Credits. (There are more, these are just the ones I can think of at the moment.)
Nope, not Miror B's tunes... but a bunch of them were redone, or bits taken from elsewhere (one little part of a song has been in all three games in fact). That and D/P/Pt used Agate Village's theme for a town as well, interestingly.