The mods cannot - we do not have access. I think the only way an admin could is if they wanted to go into the database itself and look at them, but that would only be if they're not encrypted (and some forum software packages do encrypt them) but this would be true with any forum and any forum software package (the database part).
As for IF they do - I think the admins have more important things to deal with than checking all of the PMs that go though here on a daily basis - nor would they have the time.
But, if you really want us to, you could CC us on all of them!
(That was a joke, BTW)