Everyone still refers to it as the Speedway ACT but it was actually changed to the Motor Vehicle Sport (Public Safety) ACT in the mid to late '80s
http://www.legislation.nsw.gov.au/viewtop/inforce/subordleg+494+1999+cd+0+Y/?dq=Regulations%20under%20Motor%20Vehicle%20Sports%20%28Public%20Safety%29%20Act%201985%20No%2024when you open the link above there is a button at the top that says 'Parent Act". Regulations have no power in their own right they are enpowered by and ACT. The regulations can be easily updated while an ACT needs to make it way through the entire Parlimentary system to be amended.
This ACT calls into force the regulations that you linked. The restrictive nature is the fact the regulations require consent from the local council, police etc or an indication from those bodies that they do not object or have any input into the land being used for motorsport.
Basically a track or circuit needs to be inspected by
a) MA or in the case of NSW MNSW - this inspection is all about competitior, official and spectator safety in relation to the racing taking place.
b) the NSW department of Sport and recreation must also licence the track (MNSW can not issue their licence until the MNSW Sport & rec licence has been issued. This inspection is carried out by the police department and is all about public safety and includes things like spectator fences, pit area fences, distances from the racing, access to and from the property, safe access to and from to the public road and even ammenities such as available toilets, water etc. The local Council is consulted before initial licencing notified each year.
Now this does not apply in the Aust Capital Territory and does not apply to non speed events such as Moto Trials and from what I can under stand Enduros were outright speed is not the determining factor.
This means that to hold the Canowindra Cup each year there are weeks of preparation required with the track set out for each of the track inspection which may not be at the same time and fees paid to both bodies.
This all came about back in the '50s with the amount of carnage that took place at the Sydney Showground speedway or more specifically the continual death of spectators when bikes or more often cars cleared the fence and hit spectators.