Sure, it can be done, but sorry, but I really, sincerely doubt that civilian traffic would keep on going in the face of war, especially in the way you describe it. The closest thing you'd get is civilian transports being taken by the military and then flown by military pilots to where they're needed. Same with other civilian traffic. If your city was being invaded, would you really be out on the streets? Did people casually drive around Manhattan on 9/11?

With all due respect, I don't like the idea. In emergencies and war, civilians are evacuated.

In emergencies and war, civilians are evacuated.

Look at the most recent major wars. Were the civs in Saigon evacuated? How about in Baghdad? Or Paris during WW2. How about the Battle of Britain? Or Berlin? Or, as an even better example, the V2 attacks on Britain. Or right here in the United States. After the 9/11 attacks, did we evacuate NYC that same day? No we didn't, life continued as normal later that day. The same thing applys to all the citys above. Citys in the middle of war often are not evacuated because they can't evacuate because of enemy troops, or they are considered safe from the effects of war. Look at Coruscant in the Episode 3 novel. The whole time the space battle was going on above them, people were doing what they always do every single day, as if there was nothing special about that day. They paid little to no attention to the battle, even as thousands of lives were being lost. Did they attempt to evacuate  the city when wreckage started falling or when the occasional turbolaser bolt would come down? No they didn't. Just because its and emergency or theres war does not mean you evacuate. Look at Cloud City during The Empire Strikes Back. Even though there was Imperial fleet above them and a small battle going on in the streets, did they evacuate? No, air traffic continued as normal. The same thing could happen to to any city. They either do not evacuate, can not evacuate, or simply are invaded to fast.

The Battlefield AI system will not support NPCs or bots doing shuttle runs.     Having automated trams or some type of automatic lift, however, might be possible.    One idea is to have a tram attached to a rotational bundle so that is slowly moves in a big circle that takes it from one area to another.  Another idea is to set up a tram so that it only moves in one direction at a slow constant speed.  Have it start at one area, and set up so that when it goes past it's destination, its destroyed by running off the active combat area, or it runs into some sort of a tram stop that is designed to destroy it.   Some sort of tram guide or rail could be used to keep the tram on course.   In GC Judicator, there were trams on tram guides, but they were not set up to move automatically.   

Of course several different vehicles set on rotational bundles moving slowly around the sky could be used to simulate traffic.   The sharks swimming around in circles in BF42 pirates are fins set on rotational bundles.   IN DC for BF42 there is map that has large aircraft on rotational bundles with mobile spawn points where you can man the weapons or parachute out of.

A buddy of mine managed to code some bombers in a personal BFVietnam mod to fly on autopilot.   He attached an invisible rocket to the planes to keep them moving at a constant speed and fixed the controlls so it would fly straight.   He set up the vehicle AI so the bots would just stay along for the ride, and use the MGs or drob bombs on targets.   So the plane would start at one end of the map, fly to a targate drop bombs and then keep on flying until it ran off the active combat area and was destroyed.

But the same idea might work to have vehicles moving from one end of the map to the other, just as vehicle traffic.  You don't need any bots at all for that.   

So, there are some possibilites, we just have to see what we can do with BF2142 down the road.