A control system is for completion installation, intervention and testing activities at a subsea location. The control system has a first control circuit at a surface location; a subsea test tree located in a blowout preventer at the subsea location, the second control circuit located within a riser extending from the blowout preventer towards the surface location; and a plurality of sensors monitoring characteristics of the subsea location. The second control circuit communicates with the first control circuit and receives the characteristics of the subsea location. The second control circuit also controls electrically powered subsea valves based upon commands from the first control circuit and based upon the characteristics of the subsea location to complete a completion installation, intervention, and/or testing activity.