i think you should be able to acheive both requirements already
musicbee.exe "c:\zzz\playlist.m3u" /Play
musicbee.exe "c:\zzz\playlist.xautopf" /Play
where c:\zzz represents the filepath where playlists are saved to in MusicBee, by default the Playlists sub-folder where the musicbee library is located (which by default is in the windows music library folder)
however for the auto-playlist i think i only recently implemented that, so just unzip this link, copy and overwrite the existing MusicBee.exe where it is installed
http://www.mediafire.com/?mtwk2unzy12