Bureaucrats can bring it back. They (and among others, arbitration committee) can access deleted articles, deletion logs etc. as they please. Undelete has its own process.

http://en.wikipedia.org/wiki/Wikipedia:Undeletion (for articles which were deleted without contest)

http://en.wikipedia.org/wiki/Wikipedia:Deletion_review (for contested deletes)

In fi.wikipedia (I am an arbcom member there) both delete and undelete are decided by a 2/3 majority vote.