Way back when, Microsoft used to host a bunch of auth servers for banks. A friend of mine mentioned an armed guard in front of the data center for that particular service.
I've worked on teams at MS where there was a (non-armed) guard checking everyone who got off the elevator, but before I joined MS I was once left alone in a room full of computers open to the Windows source tree, wearing my "do not leave guest unattended" badge.
Mileage might vary and all that.
Microsoft owns the data center the code lives in and certainly takes care of physical security.