So, IG attacks a Ghost from the rear. The Ghost has no shuttle equipped, but does have a dorsal turret.

The Ghost shoots the dorsal turret at R2, the IG is in rear arc.

As the Ghost has no shuttle equipped, does Autothrusters trigger?

The issue is that although the rear arc is a printed arc, it is only valid for Torpedoes with no shuttle equipped. So, does it count as a firing arc?

I have been playing it as yes, so no auto thrusters and tactician triggers, but now I think I'm wrong.

Help!

The special arc is a firing arc, whether you can shoot out of it or not. Autothrusters and Tactician say "arc" and don't specify any particular type.

As far as we are aware, a printed arc is a printed arc. Autothrusters don't trigger at range 1-2 in the ghost's rear arc.

You could look at a Firespray with blinded pilot. The arc still affects autothrusters even though the ship cant attack...though since the ship cant attack, it wouldnt be in a position to use autothrusters