I converted my playlists from mbp to m3u format for compatibility with my other software. However, it appears that MB does not follow the protocol for M3U files. It should look like this with the title separate from the filename:
#EXTM3U
#EXTINF:317,Space Oddity - David Bowie
\Music 1\David Bowie\Changeonebowie\01 Space Oddity.mp3
#EXTINF:232,Back On The Chain Gang - Pretenders
\Music1\Pretenders\The Singles\08 Back On The Chain Gang.mp3
...etc...
But instead, it's just a list of the filenames with their path!