Betfair (Click here to open account and get £25 FREE) has a separate operation in Australia. All Australian sports are available on Betfair Australia website. Australian sports market are not visible on main pages on BF main website. If you are browsing through the main pages e.g. Cricket on BF main website then you might not find BBL matches.
In order to find BBL markets follow the steps as described in following screenshot. BBL markets are available under Exchange->Cricket->Big Bash League 2015/16 -> Fixtures and then navigate menus to find market.