pretty crazy shit, imo
http://blog.wolfire.com/2011/03/GDC-session-summary-Battlefield-3-Radiosity     
 
and some more, more complicated stuff straight from DICE's GDC talk
http://publications.dice.se/attachments/Christina_Coffin_Programming_SPU_Based_Deferred.pdf 
 
a little disappointing to find out the muzzle flashes won't affect the radiosity. was hoping to light up a whole house with my gun
"Even with all these simplifications, Enlighten is not fast enough to do per-frame radiosity for a whole level. For example, if you move the sun in the editor, it can take a few seconds for all of the lighting to update. This problem also makes it impractical for instantaneous light effects in games, like muzzle flashes or explosions."

yes, I know they'll still light up the room. i just said it's a shame they aren't included in the radiosity, to indirectly light up the next room over, or up a stairway