Yep, the switch in the front only enables the rear controls. Turn it on and what ever is set on the rear consoles will result, turn it off and rear consol and fan goes dead.
There is no turn off valve for the AC and heater core flow, so warm water is always flowing to the rear heater core and if you turn on the AC the refirgerant will be flowing to the rear evaporator as well. Nothing comes out until you press the front switch to give power to the rear console which will open/close the blend doors and/or turn on the fan. The rear AC, if there is no air blowing over the evaporator, there will be very little heat transfer, that will cause the expansion valve for the rear evaporator to just close almost completly, and thus very little refrigerant actually flows to the rear evaporator. If you turn the fan on and change the blend doors to blow air through that rear evaporator, it wil of course start to transfer a signficant amount of heat, which will cause the thermal expansion valve to open to allow refrigerant flow to the rear evaporator.