Let's talk a bit more WHY they compliment Bobby's IEM's.
I goto Sensaphonics in Chicago and have the same thing Bobby has their 3D active ambient:http://www.sensaphonics.com/?p=363
What this does is 2 fold:
1 - brings in a feed from the monitor board
2 - it has microphones on the earpieces and an amp in the body pack with an attenuator so he hears the whole stage but quieter in 4db increments.
This works in tandem with a body pack like a Shure so he has volume controls from the board on that along with attenuation from the 3D so complete control.
So I'd speculate that this is less about the "feel" that folks say and more about him represented in both mixes.