In vy/vz commodores there are 4 wires going to the key barrel: constant, accessory, ignition and start. But you need the transponder key to activate the ecu and get the car started.
You shouldn't get power for car kits from there anyway, if you pull down the left hand side of the centre console trim there is a 6 pin plug with constant, ground, accessory, radio mute and audio inputs.