Running Asterisk 1.8.11 CMD MP3Player refused to work on Streams so I figured out a hack.
MP3player calls /usr/bin/mpg123 and pass arguments (never did figure out the string syntax)
When a local file is called the filename in MP3Player(FILENAME) is passed as $8 $ARGV
So here is what I did
sudo su to gain root if not already
look to see if mpg123 has been moved to mpg123.bin under /usr/bin on Ubuntu 11.10
mv /usr/bin/mpg123 /usr/bin/mpg123.bin
if already moved then /usr/bin/mpg123 will be a symbolic link so
mv /usr/bin/mpg123 /usr/bin/mpg123.bk
chmod +x /usr/bin/mpg123
next move any MP3 files you may want to play to this directory
mv /path/to/file.mp3 /etc/asterisk/radio/file.mp3
next make new FAKE mp3 files
/usr/bin/mpg123.bin -q -s --mono -r 8000 -f 8192 \ -Z URL_FROM_INSIDE_PLS URL_FROM_INSIDE_PLS
/usr/bin/mpg123.bin -q -s --mono -r 8000 -f 8192 \ -Z PATH_TO_FIRST_FILE PATH_TO_SECOND_FILE
next make the fake mp3s executable
chmod +x FK_*
chown -R asterisk /etc/asterisk/radio
chgrp -R asterisk /etc/asterisk/radio
next we add the extensions to extensions.conf create a different extension for each stream you want to create.
exten => ###,1,Answer
exten => ###,2,MP3Player(FK_filename.mp3)
Now just restart Asterisk and you can test by dialing in the streams will play over the phone!
For some reason Asterisk needs to be restarted after you change mpg123.
Total Hack but I just started with Asterisk in june of 2011.
Thought I would share;-)