Like the previous response said, expressway and tollway responses in the area are dictated more by access than jurisdiction. These days this is true for a lot of fire/EMS responses anyway but it has been the case on the highways for a long time.
It is easier for some equipment to get on and off a highway than others so they divvy up the responses. The various agencies agree that certain stretches of highway are protected by specific FD's even though it may fall outside it's primary response area or city.
For example, Winnetka's engine covers I-94 NB from Tower Road up to someplace on the Eden's Extension, to Waukegan Road, even though the entire highway is outside of the village. Part of this is due to the RED Center response system where political boundaries play less of a role than who is closest and part is due to the ISP, IDOT and ISTHA agreements in place.
Since there are a lot of ramps in only a single direction that plays a part in determining who goes where as well.
I am pretty sure IDOT, ISP and ISTHA have contact lists for each stretch of road to request fire and EMS responses. Areas like the North Shore are pretty easy, call RED Center and let them figure out who goes. Probably the same in DuPage, just call DuComm or in the NW, call NWCD. The direction where the crash is makes a difference in many places as well.