Ships will fire if they have anything in their firing arc whether they are moving or not. This is most apparent with capitalships because they have weapons in many banks (often even in the rear so as they retreat you will see them firing back). You don't see this as often with frigates because most of them only have front firing weapons with narrow cones.
In my experience this works if ships are moving, but
doesn't work if the ship's current orders are "Attack X." Any weapons that can't fire at X won't fire at all.
This is easy to verify. Fly a Kol into a pack of enemies, say A, B, and C, by giving a move order into the middle of the pack. You'll notice that the Kol will fire at all 3 targets with whatever weapons are able to engage. Now right-click on a target, say B, to order the Kol to attack that target.
The Kol will
immediately stop firing at targets A and C. All weapons that can fire at B will do so, but any weapon that can't fire at B will not fire at all, even if they could fire at targets A or C.
If you then right-click some empty point in space, thus replacing the "Attack B" order with a "Move to position" order, then immediately all weapons will begin firing at whatever targets lie in their firing arcs.
