The airbag computer is independant from the injection computer so you should have no problems swapping it over. However, if your car is equipped (and I cant tell from here) with a factory fit immobiliser then the ECU you are swopping may not be compatible with the decoder box. To tell if you have the immobilser, open the car, get in and then lock the doors with the PLIP (press the key head to lock the doors) If the car will not start, then you have an immobilser. If the car starts then you dont have the immobiliser. To overcome the immobilser problem would involve changing the injection computer, the decoder box and the donor cars PLIP head(s).
The air bag will be deployed under the following criteria.
The vehicle must be travelling in a forward direction. The speed will need to exceed 20 mph (I think)
The frontal impact will have to be within a 30 degree angle of the centre line of the vehicle (15 degrees left or right). The air bag will then deploy smacking you fairly and squarely in yer face!

But a lot better than head butting the steering wheel!
Hope that helps
Bob RTE