OP:
Are you trying to listen to the trunked system? If so, whether or not you will hear Milwaukee County traffic is dependent on which subsystem (site) you are listening to. If you are listening to the Waukesha County site, there is much you will not hear because it's not broadcast outside of Milwaukee County. If you are listening to the Milwaukee County site and have good reception, you'll hear anything on WiPSN you're trying to listen to.
If you're trying to listen to something else, there are many variables.