Well, when I worked in the OR a ways back, I knew that virtually everyone in my unit (and the CF, apparently) had enhanced clearance. In all my course loading notices, it had the security classifications of all candidates, and the only time I saw either "unknown" or "enhanced" was the one candidate on my PLQ who was in INT. I asked him about it, and, while he was rather vague about the exact classification, he mentioned having at least Secret clearance while he was overseas. Also, when I was on basic, my Sect Comd had recently returned from overseas, and when he taught us about security classifications, mentioned his was upgraded to Secret (or maybe it was Top Secret, I don't remember, but it was impressive at the time).
But to answer your question, typically, no, you won't know everyone's classification. But, if you're in the reserves with a unit that isn't privy to classified documents on a reguar basis, most people will not have the clearance. However, if you're working in a brigade, area or NDHQ, chances are a lot higher percentage of people will have it. As for me, I was curious about the way the different classifications worked and who gets them, so I picked my INT coursemate's brain for a while.