My avatar overtext might have something to say...
You were expecting a clever overtext, didn't you?
From RnC FAQ :
Q: If there are 2 cars in the same lane in front of me and I want to use the Machine Gun, can I shoot at both cars? Or do I only shoot at the one closest to me?
A: You may only shoot at the closest vehicle, i.e. you need a clear line of sight. Also you would only be able to squeeze off a round at one vehicle, as you would then need to put the weapon back into Activate position. This would need to be done on a subsequent turn, as you may only
activate each weapon once per turn.
So the answer seems to be "no", and thematically, it makes sense to need line of sight when firing a machine gun.