There have been a few meta-analasys of different things people supplement..meaning creatine (i think), glutamine, arginine...stuff like that.
But nobody does studies on some muscletech product or what not. Maybe we should define our terms in this case. Many people when they say supplements they really mean "name brand designer supplements" becasue that is what the marketing world has taught them to view them as. Well...there is no "study" that's going to back up your designer supplement.
You got to research each component and then determine it it's even dosed effectively among all other considerations. The "shotgun" approach is common in supplements. Basically you fill the sup with tiny amounts with everything you can get your hands on that has ever been mentioned in the muscle building world