Auditing with Power BI has been available for a few months within the US and more recently within all regions except Europe and Australia as a preview. This provides auditing on certain events to understand what your organization is doing with the service.

The new activity that has been added is when a free user signs up for the 60 day Power BI Pro Trial within the Power BI service. This activity is called OptInForProTrial.

In this video, I show you how you can use PowerShell to assign Power BI Pro licenses based on those audit log entries.
Full Blog with PowerShell script

Extra Video:
Additional Options for automating Power BI License Assignment –