Depends on where the firefight starts. Think urban where the troops are among the populace before the fight initiates. To your point about firefights, the enemy liked to target the dude wearing a backpack radio or the HMMWV/MRAP with extra antennas on it.
I was informed prior to deploying downrange that my guys were to wear the ABU when outside the wire. I asked if it was a good idea to have my guys wearing something made for 72 degree cubicles that melts to ones body for combat operations in a desert. I was then told to just pick up my container of crayolas and do as ordered. Officially, I informed my guys of the order. Unofficially I made sure they would not be permanently wearing ABUs if things went sideways outside the wire.