.cab is limited sales opportunity, .agency is better but acceptance of new gtld's will be the battle, google the two words and contact the two page results, best offer, if any will be the value at this point, good luck
Probably not the best investment ever...But your theory could work out. Regardless, I don't think I would renew it! Start emailing taxi companies in Brisbane and maybe you can push it for your money back or a small profit. I wouldn't ask more than mid $XXX if you found an interested party though!