I have just chased this all the way to the department of finance and they confirm what Tharra has written above.
The levy will come off all the insurances that you currently hold (if they have the levy) and a charge will be redistributed to you on your rates bill, according to your Unit Entitlements.
The man from the Ministry says some people will pay less and some may pay more but the difference will be minimal. Here’s a link to the relevant NSW gov page.
FYI: The intention is to make sure that those people who don’t have home insurance still pay their share for fire services.