The use of Asterisk/Digium is becoming more common. There are several ways to connect a Digium to a Mitel 3300. I know you can use SIP trunking and it works well but can be expensive. You can use an NSU to TE120 card in a Digium which works very well also. Both of these will also pass caller id. What is everyone else doing to connect the two platforms.

PRI converted in Asterisk to 23 channels of a T1 and passed to Mitel 021 T1 card. It will handle CID if the software is light 15 and on up. And 021 cards are cheap and plentiful!