I'm pretty sure their not after MTBers just moto bikes. As long as you ride on eastern side of the highway you will be right just stay off water board side there's enough signs to warn you anyways.
This is was taken out of [PDF]
NPWS - Illawarra Escarpment State Conservation Area issues paper ...
www.environment.nsw.gov.au/.../pomIssuespaperIllawarraescarpmen...
Also if you go to the NPWS and look under IESCA it will tell you where to ride MTB.
3.5.2. Public Access
Some sections of the IESCA are landlocked by privately owned land and cannot be accessed without the permission of neighbouring landholders. This may limit the usage of these areas of the reserve.
3.5.3. Public Safety
The IESCA contains features such as cliffs and mining facilities that are inherently dangerous and need to be managed to protect public safety. Some walking tracks and lookouts will be maintained and signposted to facilitate safe and easy access by all users, whilst other less formed, more remote access routes will give people a sense of achievement, isolation, and solitude. Access routes such as walking tracks and management trails within the IESCA and other NPWS reserves within the region are managed to meet this range of user needs.
The IESCA includes lookouts and walking tracks along the top of the escarpment. The NPWS recognises that fencing off natural features near these sites may detract from their appeal. Reasonable safety measures will be taken based on the expected usage and risk. Safety measures are reassessed following any incident. For example, the August 1998 severe rainfall event and the 2002 bushfires both caused damage to a number of locations within the IESCA. To reduce risks to public safety, it was necessary to temporarily close some areas until repairs could be completed.
People undertaking adventure activities in the IESCA expect that there is a certain degree of risk involved, however these activities may also endanger other users. For example, rock climbing and abseiling may draw spectators to hazardous locations and mountain biking on downhill bushland trails can achieve high speeds and the steep slopes and poor visibility hinder evasive action.