Can the Smart thermostat premium in the Premium gateway be used as an automation for switching other actuators or automations?

Yes, that is possible. The sensor of the Smart thermostat premium can be used as an event in routines, for example to switch on an air conditioner or fan when a certain temperature is exceeded. You can also have the Premium gateway send you an email or push message when, for example, the temperature in a room falls below a certain level.