When the application is running the application will receive region and ranging events directly. Region exit events can take up to a minute, however an entry event should be quick (~1 second).
The application will also receive region and ranging events when in the background as long as:
If the device has been put to sleep the entry events may take a little longer but they will still be received. The ranging events will also not neccessarily be as consistent as when the application is running in the foreground.