This is very interesting. Mitel has spun off a company called MKC Networks (formerly Mitel Knowledge Corp) to focus on VoIP solutions built around the e-smith server. I heard about this through a posting on the Contribs.org site:
I have asked for permission from the company to offer all of you a 5 User license for your own copy of the 7000CS communication server. For those of you who don't know what it is, it's a SIP based PBX/Router that runs on top of the SMEServer. It has integral voicemail, auto-attendant, Back-to-back User agent, call router, SIP registration server and much more.
This is a great. An easily installable, almost off-the-shelf solution for branch office networking and VoIP. Heck, the pricing is almost cheap enough that you could actually bring all the components along for a demo.
Update: now this makes sense -- Pingtel announced it's open sourcing all it's SIP-based IP-PBX stuff. Mitel has some advantages because of their familiarity with the e-smith platfrom, but they never leveraged open source as well as they could have.