Code:
alias BF.getkey {
  var %r = $regex(BF,$1-,/\(BF2:11\)[:\s]*((?:\d+\s+)+)/i)
  return $regml(BF,1)
}


Sample usage:
Code:
alias showkey {
  ;$1 = channel
  var %topic = $chan($$1).topic
  if ($BF.getkey(%topic) != $null) echo 3 -a Key- $v1
  else echo 4 -a No Key Found
}


/showkey #your_chan

Matches all the given formats,
(BF2:11) 01 02..
(BF2:11)01 02..
(BF2:11): 01 02..
(BF2:11):01 02..

-genius_at_work