ZAU Controller voiced concern regarding the on-going failure of C90 controllers to accept timely hand off's; indicating C90's choice of RADAR sites; i.e. coverage limitation/s; might be a causal factor.

Narrative

I am not filing this report because of one isolated event. This is an ongoing unsafe situation at ZAU. It involves hand offs being taken very close to the boundary by the C90 controllers. Recently the controllers in my area were briefed that C90 has RADAR limitations. They have two RADAR sites and can choose which RADAR to use. They cannot see for more than a few miles inside the BEARZ sector on a west flow. One RADAR site offers more coverage outside their boundaries but they do not have to use it. The choice is up to C90 depending on where the traffic is heaviest. I do not believe that either site complies with the 7110.65 requirements of amount of airspace one must monitor outside their boundaries. The end result is this; frequently C90 does not take hand offs until about a minute from the boundary. At that point it is too late to turn a plane away from C90's airspace without violating C90. I asked management if we would get immunity from airspace violations since they are not doing anything about the situation. Of course; the answer was no. This situation is unsafe and needs to be addressed. ZAU and C90 are ignoring the situation and brushing off our concerns. Recommendation; a way needs to be found to have C90 take hand offs sooner when on a west flow; or immunity from air space violations need to be granted.