I am pretty sure the answer to this is 'no'. The instructor should only be able to see what relates to their course.
However, Moodle is big and complicated, and to be absolutely sure would require testing or code reviewing. You could do some of that testing yourself. For example there is a demo site at http://school.demo.moodle.net where you can log in with teacher and student accounts, and see what they can see.
The other thing that makes it complicated to answer your question is that Moodle is a very flexible package. So, even if it works a certain way as standard, the administrator could change the setup to give teachers more permission. (E.g. if you just give all teacher admin permissions, then they can see everything, but that is not very likely.)