It's controlled by a dual element throttle position sensor at the throttle pedal and a feedback stepper motor at the throttle body. The ECU reads the position of the throttle pedal and positions the stepper motor accordingly. GM has been doing it for a long time with good results.
My 2002 Avalanche 2500 8.1l has it as well... Buddy's 2003 GMC 2500 has it on the 6.0l engine. Pretty sure that the same holds true for the Cadillac Escalades.