Your MCD will probably need an upgrade
From UC360 latest release notes
The UC360 release 2.1 supports the following Mitel products:
MiVoice Business (MiVB), formerly Mitel Communication Director, for audio and video
- Supported only with release 5.0 SP2 or later. For wideband codec support with MiVB 6.0 release, please refer to Wideband codec support with MiVB 6.0.
- A license will be required. The UC360 license is the same as a regular IP phone.
MiVB 5.0 SP2 introduces a new device type: UC EndUnit, which uses the SIP Capabilities Form 71 by default.
At the time of writing these Release Notes, the Form 71 programming is not suitable for UC360 deployment and a UC360
specific SIP Capabilities Form needs to be created based on the information in the UC360 Administration Guide. When configuring the UC360 extensions, it is
required that the UC EndPoint device type is selected and the UC360 specific SIP Capabilities Form is used.
MiVoice Office, formerly Mitel 5000 for audio only
- Supported only with release 5.1 SP4 or later.
- Requires a Category F SIP license.
MiCollab Client (MCC), formerly Mitel Unified Communicator Advanced
- Supported only with release 5.1 or later.
MiVoice Border Gateway (MBG), formerly Mitel Border Gateway
- Supported only with 7.1 SP2 (7.1.24.0) or later. UC360 units can register, access an LDAP database and upgrade software through the MBG.
MiCollab Audio, Web, and Video Conference (AWV), formerly Mitel Collaboration Advanced
- The new MiCollab Conference app is supported with AWV released in MAS 5.0 SP1 (5.0.116.0).
You may be able to make it work with a generic sip extension and 2 Multicall appearances of its own number set to ring but it would probably not be supported.
If I never did anything I'd never done before , I'd never do anything.....