Ok, I figured this one out:
Just edit the 'class.ticket.php' file, go to the function called 'postMessage' andadd the following code directly before the 'return' statement at the end of the function:
$to= "you@yourcompany.com";
$headers = "From: from text goes here\r\n" .
"X-Mailer: php";
$subj= "Support Ticket Updated by Client ";
$body= "This is a notification that Support Ticket# " .$this->getExtId(). " has been updated by the client. http://" . $_SERVER . "/view.php?e=" . $this->getEmail() . "&t=" . $this->getExtId() . ".";
mail($to, $subj, $body, $headers);
Cheers,
Steve.