Is it possible? Yes. Is it simple? Not really.
The only way I can think of being able to do this is to add a device outside of the dock to do your reporting. It would have to be something that would detect a laptop being attached to the dock, without affecting the performance of the laptop.
I've considered the different ports involved in a dock, and everything could be considered a security issue except the power plug.
So, my proposal is to use a meter on the power cord to see when there's a spike in usage. I know there are devices out there that can do this, but I'm not sure if they could report to you the information you're looking for. If this were me, I'd rig up an Arduino to measure the current going to the dock. At a certain level, count it as being used, then when it drops below that, mark it as unused.
Using an Arduino with built-in wireless and a dedicated router to do communication with a central hub, you can get your reports. This requires electrical, electronics, and programming skills to accomplish it, but it shouldn't be too bad. (Famous last words, right?)
Use a small enough Arduino and the right enclosure, and you could make it so the user would be very unlikely know it was there. Of course, you'd have to get your company's permission to do something like this.