You will find here an interesting article on security and Skype for business deployment written by Sense Of Security. To resume nothing to worry about but some good recommendations. This White Paper could be useful to reassure a concerned a It Manager. https://www.senseofsecurity.com.au/sitecontnt/uploads/2015/12/Sense-of-Security-Whitepaper-Skype-for-Business-Security-V1.0-17Dec15.pdf
Regards
Laurent Teruin