I've been flying with no tracers recently but have found that in a gunner position in a bomber you can still see tracers from the other guns firing even though the gun I'm at doesn't show them. It would be nice if there were no tracers shown from any gun on a bomber when you have no tracers selected. That would bring a nice element of surprise to an enemy on your 6 who may think you are afk or do not see them as they approach you. 
Regardless if you're a gunner in a bomber or in a fighter, you will see any friendly plane's tracers when they fire, even on the drone buffs in your formation. The enemy won't see the tracers however if you have them turned off.
ack-ack
