That radio chatter is dubbed in afterwards and made to sound like people talking over headsets, except nobody talks like that! Pretty much all of the E3 gameplay trailers are fancied up though... The BF4 one was definitely scripted... nobody seemed to die, and it had A.I. boats, choppers that did exactly what they wanted etc. If they don't it could end up being a complete shambles like the Assassins Creed or the Thief playthroughs.
I'll remain sceptical about this... all too often the E3 footage we see ends up being nothing like the end product. I can't see how they'd be able to keep up that amount of detail throughout the whole of NY, even if it's just Brooklyn and Manhattan that's featured. Plus if it supports lot's of players it'll just end up being like GTA IV's online deathmatch where it's full of 12 yo wannabe gangsters...
