I received a response today from IDOT regarding Broadlands Road (200N / State Street). While I am not thrilled with the response, at least the department responded promptly. The gist of the letter seems to be that IDOT will do only the barest of maintenance to roads like this except in cases where the Department can dump responsibility for the road onto another jurisdiction. However, once another governmental unit accepts responsibility for a road, IDOT would likely have no future obligation to repair it.
The letter is here: IDOT-letter