If someone is looking to integrate to Elastix MT, I will recommend to stay away for production environments.
Elastix MT doesn't work and the real production looks a bit stuck behind in time.
Here are the last updates so far from Elastix
asterisk Jan 2016
kamailio Dec 2014
elastix Dec 2014
elastix-framework July 2015
elastix-pbx July 2015
There is a problem with elastix, extensions and trunks where they dont work. There is some crazy work around to get it working using one NIC for extensions and separated NIC for Trunks, then the extensions will work if you are lucky.
How about integration with Vodia Networks? www.vodia.com