Australian/NZ Standards are not law. Australian Design Regulations that reference the standards are law.
This is true, BUT in state electrical legislation (not the ADR) there is a clause stating that electrical installations must comply with the wiring rules. And the wiring rules is AS/NZS 3000, so if someone creates an electrical installation that does not comply with AS/NZS 3000 then they may be prosecuted under the relevant state legislation. So while it is true that AS/NZS 3000 is not law, failure to comply with it means that you are liable to prosecution under state law.
It is also important to note that every state has a slightly different interpretation of what constitutes an 'electrical installation'. For example in Victoria a caravan is classified as an appliance, so exempt from AS 3000 and AS 3001. This is one of many reasons why most caravans are made in Victoria.
With testing and tagging, the relevant standard is AS 3760, which is not referenced by AS 3000, but is often referenced by WHS or OHS legislation depending on what state you are in. Interestingly in QLD, there is an exemption in the Electrical Safety Regulation whereby you don't need to test and tag your equipment if the circuit is protected by an RCD. Many offices including government departments don't test and tag because of this.
For caravan parks they are private properties, so if they want to enforce a test and tag rule that is up to them. There is no legal basis for it, but if they make it a condition of entry then that is their business.
Where does the air come from, Electric or petrol compressor?
Engine driven compressor, usually mounted on the back of a ute, or they use the plant air which the company supplies. It is pretty common on mines now to ban the use of 240V tools in wet areas or confined spaces. There is usually a battery charging station in a workshop or similar in a place that isn't prone to getting wet.