It is illegal not to have a current electrical warrant. Anybody not complying is breaking the law. If a fire ensued questions would certainly be asked.
Illegal not to have a electrical WOF or illegal when you connect mains power to the camper motorhome, that does not have a electrical WOF? For as long as i've been living in NZ, i've never bothered having electrical WOF for our camper van for the simple reason, we don't connect to mains power.
We've just imported a new RV from the UK and despite the registration guy doing inspection asking about electrical WOF, I have no intentions of doing so. The electrical standards in the UK on these motorhomes IMO are more strict than what is allowed in NZ. I was surprised to see full RCD breakers in the order of how new houses are wired in NZ today. When the test button on the RCD breaker stops working, then that's when it won't pass electrical WOF, any more tests that the inspector has to do every 5 years is just a cash grab.
Related to the OP, my friend just imported an Airstream from the US (2010 model 20 footer). He went though all caravan and electrical compliances which was pretty straight forward. In meeting his electrical compliance, he just left the Airstream in 115VAC and uses a massive step down transformer. Massive in that it weighs over 20 kg rated for 8kVA ; complete overkill. But eitherway the use of the transformer brings another level of safety to his setup (being the transformer serves also as an isolating transformer).
Other compliances you may consider is the LPG. I've heard of other caravan importers going through an expensive inspection on LPG (again, IMO a cash grab on brand new camper / motorhomes). I can understand if the vehicle is old and thus yes, the lines should be tested, but on a brand new build ; it seems senseless. I'm talking on a brand new motorhome, the importer having to spend thousands just to check, replace fittings. It seems that these compliance guys spend a lot of time taking panels off to see how the lines were routed, etc.