So for years they have had interop systems like CLEMARS, CLERS, OES Fire Net that are rarely utilized, what makes you think CRIS will be utilized?
Where I live the agencies and their dispatch centers are all linked via the state's microwave. It used to be linked with 450+ MHz frequencies, but is now all on the state's system. It is known as "the hotline." Even Cal Fire's San Bernardino ECC has access to it. We don't have CLERS in Inyo and Mono, but there is a need for direct, intercom type communications between dispatch centers. I think that the use of CLERS is low because it is not private. Mono County also has a link to Alpine Co (which is dispatched by Douglas County, NV) so there is a Douglas County to Mono County link. It is on 450+ MHz.
CLEMARS is used as a tactical frequency by the SO's and the PD's. It is also used for interagency contact when units are in simplex range. Different agencies communicate on all the law enforcement and fire nets. Both counties have a mutual aid repeater system on the same frequencies that has widespread coverage. There are two frequency pairs at most of the repeater sites. The mobile of the other repeater site is used as a tactical.
CALCORD is used when non law enforcement personnel respond to incident scenes such as when the road departments, non LE USFS personnel and county health might be players. We see it used during floods, avalanches and the hasty stage of SAR's.
The eastern Sierra counties already have their "CRIS" system and don't need trunking and a computer controlled cross band system provided by the state.
The only exception to this is individual vehicles and heavy equipment of Caltrans don't have any communications with much of anyone else. The station superintendents have CHP radios and the CHP can communicate with each Caltrans vehicle. State parks, at least the park rangers, have a VHF High mobile in their vehicles. I don't think their handhelds/extenders have anything but 700/800 in them or access to other bands. . State Fish and Wildlife warden's hand held extenders are tied into a VHF-High mobile radio so they have handheld access to all the mutual aid type and other agency frequencies on that band on their handhelds.
Perhaps rural areas are more accustomed to working interagency on a frequent basis given no one has a lot of personnel/equipment. During large events we can see law enforcement officers from 7-8 agencies working together*. However, rural areas don't really need CRIS. VHF-High works better in mountainous terrain. We've already worked out most interoperability needs.
*U.S. Forest Service, Bureau of Land Management, National Park Service (more often in southern Inyo Co.), State Fish and Wildlife, State Parks (more often in Mono County), CHP, Mono County SO, Inyo County SO, Mammoth Lakes PD and Bishop PD.