I've heard B-52 cabs used as part of a PA several times. Medium small venues,  really little place for bass frequency loss, 15's positioned low.  I have to agree with Lonman on this...They were plenty loud, yet I just didn't like their delivery of the bass frequency.  I'm more impressed with Peavey, or Yamaha than that make speaker.  I liked the rugged build of the B-52 cabinets. nothing more
I'm no soundman, nor am I a tech. Yet I will tell you from my own personal experience...(at least for band purposes) medium indoor doesn't compare with "outdoor" venues.  My cabs/heads that will fill even a medium large indoor venue,  often lack the headroom needed for outdoor playing. For outdoor venue's I always went with a better projection cabinet. Usually a folded horn type bass cab.
Depending on the outdoor terrain, it's amazing how sound can get lost.
What type of outdoor conditions ?  
 I've been pretty spoiled by having the pleasure of going thru Altec VOT stacks, those cut outdoor fine 
