The V-Call/V-Tac channels are in every STARS radio system wide. And, the 700/800MHz national interop channels (NPSPAC) channels are in every STARS portable. The programmed capability is there.
The problem from my perspective is that STARS Management, Systemwide, has failed to put into practical use protocols for the use of the wide variety of Interop channels and frequencies available to STARS users. Like others have mentioned, the only folks who understand those channels intended use are "radio" guys like scanner enthusiasts, hams, radio-techs, etc. The average user is clueless.
The further problem in my view is that this situation is common in all of the sizable systems I've had any contact with. The whole interoperable plan post-911, in practical day-to-day use, just hasn't come together as intended, expected or required...............