You can definitely seperate the power busses. I think what Bob is saying is that you never turn the gyro "off" in flight. Even when you switch the gyro off the servo signals are still going through the gyro, either the hardware or a combination of the hardware and the software depending on the way the gyro is designed.

I have used the BL-3GRC on an EDF. It works well but even the designer recommends a separate servo power bus for any decent sized model.