How to connect Mitel 3300 ICP to TrixBox 1.2?

We have a Mitel 3300 ICP system at our corporate office with about 250 2XXX extensions (most of them are using Mitel 5220 IP phones, which is probably not relevant to the question). Few days ago I created TrixBox 1.2 on one of our servers, as of now it has almost 10 1XXX sip extensions (they use X-Lite phones, Mitel 5220 SIP phones and BlackBerry 7270 WiFi SIP phones) which work perfectly.
What I want to do to connect those 2 systems, trunk the somehow and looking for the easiest ( I am a TrixBox newbie) and the best way to do it. I do not have any hardware purchased yet, so any ideas would be very helpful also if somebody can point me towards some guide of how to do it, configure it on TrixBox side I would greatly appreciate it.

My ultimate goal is to connect those to systems so if somebody with 1XXX SIP TrixBox extension dials any 2XXX Mitel extensions it will work, and vice versa. :question:

check this link for a working SIP Trunk Config between Asterisk and Mitel 3300 ICP - … tml#000000