I have a an angular event like this:
$broadcast the event, listen for it in your other controller with
$emit another event on completion, and listen for it in your original controller so you know when it is finished.
I would not recommend this approach. Instead use a service.
Emit and broadcast are coupling your mechanisms for communication to the view because the $scope is fundamentally a fabric for data-binding.
The services approach is far more maintainable and can communicate between services in addition to controllers.