Because no-one saw this coming....word is they will be ATR-72s, I am almost certain we will see them in Canberra replacing the E170s which will shortly be leaving the fleet.
http://www.asx.com.au/asxpdf/20110110/pdf/41w3df1l79dkrn.pdf (http://www.asx.com.au/asxpdf/20110110/pdf/41w3df1l79dkrn.pdf)