Tanzos;d-218242

What if you bring both GBA and ARC Trooper, but the turret us destroyed. Will GBA be able to summon the Brute if ARC Trooper's turret is gone?

Just to officially confirm what folks are saying in here already. Yes, you would be able to summon the Geonosian Brute if the Blaster Turret is destroyed and there is nothing else in the summon slot (such as the Rocket Trooper). The priority part of that post really only applies at the start of the encounter where both units are triggering their summon ability at the same time.