I don't remember anything specific about that, personal property is certainly never inspected. The thing is that you sign a NDA at the start of your employment, even external vendors have to, so you're trusted to act responsibly. And there's absolutely nothing different between accessing corporate data from your home or your office computer: People who really want to could copy their corporate emails, whole shares of corporate applications or repositories of corporate data to USB devices on their workstations or external hard drives. The fact that they don't do it and that there are virtually no leak from employees or vendors show that this trust responsible relationship works.Even so, there is still corporate interest in what data someone actually has on their hard drive...when said hard drive goes missing or someone quits, yes?
It always makes me laugh when people speak of Microsoft as the next Big Brother. Sure, there could be some questionable decisions from time to time in such a big company, and there has been a few bad ones in MS earlier history, but internal employees are just as quick or quicker to pick up on that. Hell, the "diversity" social groups have even forced Microsoft to withdraw support to some politicians who didn't fit in with the corporate anti-discrimation policy! ^-^