Needed to have a Lync client running on another machine for testing. All I had available was my Linux workstation. Yes, it works.
Basically you need to first install the pidgin-sipe and purple-sipe packages to add the Office Communicator protocol. These were readily available for Fedora 20 with yum.
Once the packages are installed you can go into the Manage Accounts dialog and add an Office Communicator account.
The fields to fill out in the account dialog are as follows:
The username is your Office 365 login. Many companies use the user’s e-mail address (in federated environments this will be set as the userPrincipalName in your on-premises Active Directory). Password is your Office 365 password (again, in a federated environment this will be identical to your on-premises Active Directory password).
Server [Port]: sipdir.online.lync.com:443
Connection Type: Auto
User Agent: UCCAPI/15.0.4420.1017 OC/15.0.4420.1017
Authentication Scheme: TLS-DSK
There are limitations to this. Basic messaging and presence work fine, as will text conferences. Anything involving the exchange of media, in particular screen sharing, audio and video, will fail. Pidgin simply doesn’t support the infrastructure required for that yet.