Well I don't know as I've never owned an automatic car. But i've heard this described.

Yes you can run a new wire into the car and under the dash. This would work, but would be better to tap into it under the hood. Check the wiring diagram it may help. I recall there is a little box or connector on the firewall just above/behind the firewall that is going to the automatic.

Which 1200 do you have? North American or Australian model?