The information that will be pushed to your calendar (after employees sync their shift calendar is based on your preferences in Settings > Scheduling > General:
Unless you toggle the filters at the top in the Schedule view:
After adjusting the filters the software generates a new Webcal URL & you can sync a calendar of a specific shift group, team, shift template or area. In the above example only the 'Sales - Amsterdam' group would be synced to my calendar.
Any changes to shift schedule will be automatically synchronised!