There is a trace flag you can add to your appserver.config that will trace session or licensing. See this thread Trace Flags
When I was on a version where that was not supported, I created a UBAQ that called the AdminSessionSvc to get the current license count. I used that query in an Executive Cube that ran on a schedule. Then you can query the cube data with a BAQ / Dashboard / EDD to do any kind of analysis you want.