It seems that the operation object can only emit 'complete' and 'error' events. I think it would be great if the object could also emit 'running' or similar event that indicate the 'RUNNING' status in all Operation resources.
A use case example for that feature is to show users that the instance is in the process of creation. It can be done manually by the method similar toOperation.prototype.startPolling_ but since there already is the function for that job, it should not be re-implemented.