Here you go http://en.wikipedia.org/wiki/Boost_c...ontrol_details

Not all electronic boost systems are Closed Loop, the wiki article has a pretty good explanation of the pros and cons for both methods. It does leave out how even with an interrupt controller, in a Closed loop system you have limited ability to fully interrupt all boost signal to the wastegate.

It does talk about the limitations of internally gated turbos, even with no boost signal the exhaust gas pressure can begin to open up the flap. At least with the hybrid control you can remove the boost signal from the equation. An EWG with a center hinged flap wouldn't open with exhaust gas pressure which is something to consider.