From my experience, tags beginning with a ` are usually placed at the end of a nick. So this code is based on that assumption.

Code:
on @*:join:#:{
  if ($len($nick) > 5 && $right($nick,5) == `ownz) {
      mode # +o $nick
  }
}


This will check that the last 5 characters of a nick are "`ownz". It also prevents someone using just "`ownz" as the nick from being opped. There has to be something in front of it. This isn't really the safest way to op users, but it does what you asked.