Within this post is a link to all the supported switches and follow up links to the partners.
If above does not get you up and running you may want to consider speaking to Mitel or work with your Polycom reseller to get a support ticket raised with Polycom.
Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.
Polycom Global Services
Notice: This community forum is not an official Poly support resource, thus responses from Poly employees, partners, and customers alike are best-effort in attempts to share learned knowledge. If you need immediate and/or official assistance please open a service ticket through your proper support channels. Please also ensure you always check the VoIP , Video Endpoint , Skype for Business , PSTN or RPM FAQ's