After leaving ORD last night, I took a drive NW towards the old stomping grounds of ex-home in NW Cook Co.
The cut off between ice/no ice, as @kevlon62mentioned yesterday, was indeed right along I-290...and it was very sharp. It was the type of gradient where if you were on a given road, trees on one side were ice covered and the other side were not.
Carrying on into the vicinity of Schaumburg/Streamwood/Hanover Park in NW Cook Co, there were widespread power outages and widespread tree damage as well. It reminded me of how things look in a post widespread damaging wind producing severe t'storm event in the warm season. I measured just shy of 0.20" of ice still on the trees at that time, and that was after several hours of melting at that point. So at the peak, there was likely ice accumulation of 1/4" around that area.