If they are using solutions from Avaya, Mitel, Cisco or Microsoft, please take a look at the following:
http://www.cisco.com/en/US/products/ps11498/index.html
Avaya VDI communicator
http://www.avaya.com/usa/product/vdi-communicator
Microsoft Lync 2013 with Lync VDI
FAQs for Lync in a Virtual Desktop Infrastructure (VDI) environment - Lync - Office.com
Mitel UCA
https://www.nemertes.com/reports/mitel-vmware-highlight-growing-integration-uc-and-vdi