A couple of Questions about Dirtside II

Here is a couple of curly ones that caused massive conflict, which I
want to clear up before I run a demo at SAGA 97 (in Australia)

1. What is the effect when a Firer System Hit chit is drawn during an
artillery barrage?

A: The barrage is a complete failure
B: The target vehical is immune from dammage?

2. Can missiles fire opatunity fire?

3. In Stargrunt II, grav vehicals act as v-tols, yet do not in DSII.
What is correct (eg , in SGII, Grav can fly OVER Trees!)

Thanks 

Darryl