Hi hightrax,
I believe the ASX penalty is $2000/day. Therefore, it may be cheaper to pay the penalty than buy the stock back, especially if the price continues to fall. In other countries, I believe they force the broker to buy the stock back. I recall an article about this regarding BNB back in March in which Trevor Lowhenson goes over this exact point...
I'm not a 100%, so it would be good if someone else could confirm...
good luck