**UPDATE**
I may have answered my own question here. So I found this in the "Engineering Guidelines":
We also use these PoE injectors for those customers who don't have a PoE switch:
Correct me if I'm wrong here but it sounds like the Mitel IP phones are capable of both "Phantom" and "Spare Pair" power. Whereby PoE Switches will use the "Phantom" type to deliver power and the PoE Injectors use "Spare Pair" type to deliver power.
Thanks,
-Iron