its because they dont fall under the old 15 yeear rule and were an australian delivered model in limited numbers
same reason why youc ant ipmport an evo 6 or so and register it for road use - because we got a handful sent out as aussie models ..
and now that the 15 year rule has changed - i dunno if they can ever be imported and registered unless its a private import ( whereas you own it in japan/nz/wherever for a year - then bring it across )