Connecting FreePBX to Mitel IP Based PBX

So I have my Asterisk PBX ( on the same LAN as my Mitel IP Based PBX ( I need the Mitel system because it integrates with my hotel lines to each room.

The annoying thing with Mitel is that they cost for every feature that is already free on freePBX. I’m spoiled with FreePBX :). But I discovered that the Mitel system has SIP trunks enabled!!! That got me to thinking of linking the two PBXs!

So what I want to do is have all incoming calls go through my FreePBX system which will be the main reservation line. Then if people want to dial to the front desk, they press 3 for the IVR, and it’ll transfer to the automated attendant on the Mitel system where they can dial to rooms directly, or press 0 for the front desk receptionist.

So, I found this tutorial:

Is this what I have to do to make the two PBXs communicate with each other?

If I set the extensions correctly, then is it possible for me to have the automated attendant on the freePBX dial the extensions on Mitel’s system?