Micorosft Lync Online team released new three usage reports for Microsoft Lync Online.
They are integrated with Office 365, and you can find them in Admin Center, reports.
These reports shows usage of Lync Online services like below:
Active users – The number of users who have signed into Lync and took part in a P2P session or conference during a reporting period.
Total audio or video minutes - Total audio or video minutes during a reporting period