Azure RMS now offers access to the Usage logs, for free. Said logs could be used to examine who, when and where from accessed a protected document, and allow you to build reports on the general usage of the service.
Getting the logs requires the use of the AADRM PowerShell module and some additional steps will be required if you want to consolidate the logs into a single file. Read the full article here: http://blog.enowsoftware.com/solutions-engine/auditing-your-azure-rms-protected-documents.