I went thru this a couple of years ago when I replaced my VHF.
DSC is mandatory in the EU and States, and to my knowledge must now be classD
http://www.vhf-dsc.info/tech.html
The data channel is CH70, which seems to be allocated in the NZ frequency spectrum to DSC.
Anyways, I was incredulous that since every VHF radio sold has DSC, that coastguard didn't monitor it; why wouldn't SAR utilise such a fool proof system of emergency location. Must surely be a simple matter of running a data log on CH70.
Enquiries with Coast guard advised me it is unsupported and when question as to the why