Capt Fathom ....They cant make it unusable - It is the RWS and must comply with MOS 139 .... therefore must be smooth and free of obstacles.
They have issued a NOTAM though saying aircraft movements are restricted to " prepared surfaces " - I can't find a definition of " prepared surface " and when I asked for clarification was told it was in the CASR'S and AIP and I need further info to call CASA ? - Still cant find it tho - even emailed Air Services - I think he means sealed surfaces ? ?