Situation: The client would like to train his new employee by allowing the employee to listen in on their phone calls.
Resolution: We can setup Mitel Silent Monitor. Quoted from Mitel:
This is the step: Enabled Barge-in and Silent Monitor. You can do this with the *codes you listed in the email or from the client software. In the software right click on the contact and select barge in or silent monitor while that user is on a call.