Using the Turbosmart "Black Box" controller for the EGate, and sending a PWM signal into the controller from the M800 with give you position control of the gate, but with no real feedback.
You could possibly build some aim tables using the Aux Tables, but this would be something that you would need to develop yourself.
Stephen Dean MoTeC Research Centre Melbourne, Australia
Did this for the eALV with blackbox and planning to use the second output of the blackbox for the eWastegate. Gives very nice and precise control of the valve opening (with Aux-table as stated by Stephen). I even linked it to another table to be able to enable/disable the behavior (Boost-setting 1 > no eALV, Boost2/3/4 > with eALV). Beware, these valves need serious power! In my case, controlled by a Motec PDM.