I also heard from an unofficial source that this aircraft was on a Charter for a company "A" who brokered it out to a company "B" who in turn brokered it out to a company "C".
Apparently company "C" had completed a trip in the accident aircraft late the previous night and when the request came in for the early morning trip to Chicago the "C" crew was unable due to duty time limits, so company "B" sent their crew (The accident crew) to complete the trip. The problem being that company B's crew was not on the operating certificate for Company "C" and said crew may not have been familiar with the CL 600.