I have integrated it with Microsoft Lync 2010 by using the same trunking method. Depending on how many extensions, dialing plans, etc., it can get a bit messy from an administrative standpoint.
This can be achieved with the Bridge and or the Generic SIP Trunk/Voip Provider setup (this allows for Outbound rules). If it supports SIP you are most likely able to. The only one that gave us a major headache was a hosted system by T-Mobile in Germany but that worked too.