This sounds like it'd be easy, and perhaps it is if you only have one or two to monitor, but watching a company of 2,000 people in this way is not such a simple task. To learn why, as IT people, we need to understand how OneDrive for Business works in Microsoft Office 365.
A basic primer on OneDrive for Business
So, how do I see what's going on in my employees' OneDrive for Business sites? I really need to know.
That being said, let's say we know that Allie Bellew is being a bad OneDrive for Business user. An IT employee walked past her desk and saw her streaming music from her sweet collection of 90's techno, she saw it, she swears! In some companies, this might be OK or even encouraged, but not in this fictional case. No music for Allie.
An IT admin decides then to snoop on Allie's OneDrive, but is met with this:
In short, since there's no simple or straightforward way to grant your IT employees access to Allie's OneDrive to see what she's up to, you have to use PowerShell to make them the site collection administrator.
TechNet has a handy guide and PowerShell scripts available to accomplish this task. The scripts will grab a list of all OneDrive for Business sites in your organization, then assign a user as site collection administrator for those sites. If IT only needs to see an individual site, the list that the first script outputs can be modified to include just that one site location.
This procedure also comes in handy if you need to enable eDiscovery for your company's OneDrive for Business sites on a global scale. If there's a legal issue, it's almost certain that this will need to be done to ensure compliance and discovery of all appropriate documents.