In Exchange, it's possbible to grant or decline users full access (and 'Send as') to another mailbox by the administrator, so the mailbox is added or removed to the granted users Outlook automatically. 

Also the granted user will see every subfolder within that mailbox without additional doing. Using the Outlook function to set access rights - which is currently the only way to grant access - subfolders have to be granted indiviually and normal users do not know the procedure to grant other users. 

Other aspect: it couldn't be controlled by administrators and so it's not possible to revoke that individual access right gained by Outlook.