I'm guessing they'll be doing the BNE-PQQ-BNE sector to physically cycle the a/c from BNE to SYD, much the same as Qlink flying the Q400 from BNE to CBR.
I'd say once the network grows and there are more a/c they'll drop it if the numbers aren't there. DJ would have the figures on how many people are flying from BNE to PQQ via SYD too to have a bit of an idea if it will work. The ATR will be able to offer more competitive pricing than what Brindy were with a Metro or the Jetstream.
Remember the days of the coastal milk run - BNE-OOL-BNK-CFS-PQQ-TRE-WLM !