According to Microsoft, Lync must be completely uninstalled, following the procedures documented at https://technet.microsoft.com/en-us/library/jj945448(v=office.14).aspx, at least for Calendar functionality to work correctly.
This repo contains a python script for removing all referenced Lync components for all normal users on a machine, i.e., with homes in /Users.
It is somewhat naive in that it assumes the users have not moved the Lync keychain items out of the Login keychain and into some other keychain. It handles the potential for multiple "your.email@domain.com" certificates in the login keychain, however. This is all done by running the security command as a subprocess. Improvements could probably be made to do this all with the Security Framework and the PyObjC bridge, but this gets the job done.
You will need to edit the pattern global APP_PW_PATTERN at the top of the uninstall_lync.py script to look for your environment's email domai