I think the way it is set up is that if you select a saved playlist, it will automatically load the .m3u to winamp, and then display in the playlist category. The commands you view do the following:
playlist play: play the selected .m3u playlist automatically (not to sure what the difference is between this and m3u play)
playlist add: add the .m3u playlist to the exiting playlist (should there be one)...or in other words, que the playlist
save playlist: more or less does what it says, save the existing playlist to a .m3u file to the xlobby/playlist folder.
clear playlist: clears the current playing playlist.
Find further info here:
http://www.xlobby.incolby.com/EventVariableSheet2.htm
Hope this helps.