I don't know about Chicago - I know where I've lived, the cops tend to respond to assault calls. It doesn't matter what mode of conveyance the victim was using, throwing eggs from a car is assault. I guess the other part of it is that I know cops, so I don't know what it would be like for someone who doesn't have cops in their social circle or something. Still, if you don't report it, you don't know how they'll respond.

Doesn't really matter anyhow, not sure how much I believe the story in the first place.