I-Call doesn't have anything to do with interop, specifically within the constraints of a Motorola system.
I-Call, as applied to a Motorola system (which calls the technology "Private Call") is a dedicated talk-path between two specific subscriber units (or a dispatcher and one specific subscriber unit).
As PDXBofH stated, most of them that you will hear on the ComNet system are dull. Very. Dull. (Portland Police use them occasionally, TriMet maintenance crews use them quite a bit, AMR from time to time, and the Portland Streetcar.)
Most inter-system links are done within the infrastructure, or on demand through patching (i.e. WSDOT to KC/VC in your example - I didn't see anything in the conventional data that looked like I-Call infromation.)
joe