As far as I remember Servo transparency is a nice name for "jack stall". It is common in smaller helicopters with parallel jacks. AS350, SA340/341/342 Gazelles etc. Jack Stall is often included as part of the flight envelope definition. Sorry, I don't know of any repositories of knowledge but I'll ask my contact at Marignane.
PS Lu, thanks for the input, I'm sure the Eurocopter Bureau D'Etudes will jump for joy.