Microsoft recently had announced a report for Office 365 ProPlus installation done by users (http://success.office.com/en-us/roadmap#R-18376) . This is something that customers were demanding since quite a long time as it was quite difficult to track how users are using office 365 within the organization. Good news is that this feature is now available, but as a part of the new office 365 portal. If your organiation is signed up for updates, you should be able to view this report. However, your tenant must be signed up for organiation wide updates. To see the process of activating the updates for your tenant. Please visit the following link https://support.office.com/en-us/article/Office-365-release-options-3b3adfa4-1777-4ff0-b606-fb8732101f47
Now lets have a look at how to see the new reports:-
Login to the portal and you shall see a link shown in the image below, if you have enabled the updates.
Click on the Option New Admin Center and you should see the new portal that appears like this:-
Click on the home button as shown above and select the reports option
Once you click on the reports tab. You shall be seeing the Office 365 Pro Plus activation reports the report shall contain how many installations a user has done across platforms. That includes PCs , MACs etc. But beware that this report might take 24 hours to generate after you activate the Organization wide updates.