My apologies Geoff..you're quite right (I just checked). Seems the ACT have some prety strict rules regarding proximity to CBD etc.
This link might help the OP
http://www.somersoft.com/forums/showthread.php?t=53025
Hi Rohan,
Im not sure about the ACT but in NSW there's 'granny flat' specific legislation which supports and promotes the type of development you're talking about.
Step 1: Find out if the NSW State SEPP applies to the ACT...