I just upgraded to trixbox 18.104.22.168 and freepbx 2.5 from an older version of trixbox.
I had a streaming MOH category
/usr/bin/mpg123 -q -s --mono -r 8000 -f 8192 -b 0 http://voxsc1.somafm.com:8502
that worked just fine.
However now when I add this MOH category 3 mpg123 sessions are created (without any active calls).
If I actually implement this category as the MOH for and inbound or outbound route. The number of mpg123 sessions increments. I had 61 mpg123 sessions actively streaming at one point tonight before I deleted the MOH category.