Yes, absolutely. In fact, based on the fact that my apps frequently sit in 'In Review' (versus 'Waiting for Review') for 12+ hours usually, it wouldn't shock me if they had multiple people review each submission.
How much they play around with the app seems to vary - I've had odd, hard-to-trigger bugs get my app rejected, even though they existed for several prior versions.
Each app submission/update costs Apple a fair amount of money to review.