The bilby is important to SA because -
South Australia forms a large part of the bilby's former range and an important part of the bilby's recovery is its reintroduction to this state. 
In 1994, the South Australian Bilby Recovery Team was formed to coordinate the recovery of this unique animal in South Australia. 
A captive bilby colony was established at the South Australian Department for Environment and Heritage's breeding facility at Monarto in 1994. 
An offshore island in Spencer Gulf was chosen for 'Stage 2' of the recovery program for 2 main reasons. Importantly, the island was of sufficient size to support a viable bilby population. It was also the largest parcel of land in South Australia that was both within the bilby's former range and free of foxes, cats and rabbits.

From the site: http://www.environment.sa.gov.au/biodiversity/bilby.html#bringing 

We have enjoyed doing the puzzle of the bilby this week - especially changing the shape of the pieces.

Once the bilby was found all over Aust, but now they are only in WA, NT and Qld. Since 1994 there has been a team of people who have been helping bilbies in captivity at Monarto and on Thistle Island so that hopefully there are more in our state again soon.
 (http://www.threatenedspecies.org.au/tsf/tsf.asp?m=2&t=recovery )