What version of the G5 do you have? VHF or UHF? If UHF, what frequency segment? As for the CFP @ Ohare, I believe they are still using the original Smartnet system, but I could be wrong about that. The G5 will not track older SmartNet systems. If you are programming the OEMC system, did you put in the proper site info a control channel for Ohare Field? Again, I don't know if they are actively using that system yet.
** EDIT ** I just noticed you stated the VHF model. Schiller Park PD is on UHF, not VHF. So you would not be able to monitor them on the G5.