Not all counties utilize the IREACH talkgroups. Some patch the VHF frequency and others don't. Most of time the VHF frequency is used more. Even in DuPage they use it to coordinate with Superior, LifeStar, LifeNet, UCAN, OSF etc.
On a scene. We use ireach to talk directly to the helicopters. Its standard practice to use ireach as a ground frequency. Although some use starcom21 and some use other methods