Non-global zones use the default scheduling class for the system. If the system is updated with a new default scheduling class setting, non-global zones obtain the new setting when booted or rebooted.
The preferred way to use FSS in this case is to set FSS to be the system default scheduling class with the dispadmin command. All zones then benefit from getting a fair share of the system CPU resources. See Using the Fair Share Scheduler on an Oracle Solaris System With Zones Installed in Creating and Using Oracle Solaris Zones for more information on scheduling class when zones are in use.
For information about moving running processes into a different scheduling class without changing the default scheduling class and rebooting, see the priocntl (1) man page.