A remote device can not be restricted to show ONLY a selected Cue view, so it is feasible for someone to mess with the main mix if they were to change the settings on their device.
A fix for this has been requested for years and has been ignored by Steinberg for years.
Despite this, the Cue mix facility in ICPro is very useful for providing musicians/singers (and drummers) with the ability to set up their own headphone mixes.