I did my checks years ago so you'd need need to email them yourself. And how can I show you that no law says you can't do something? Sorry I'm not going to argue further, I'm happy with the checks I did and I'm happy towing with my unplated imported truck.
For post 1997 i believe the law is more explicit that you can only tow with a type approved vehicle.
Not arguing, just trying to get to the bottom of a very complex situation. I deal with so many people that claim to have found info / a law re an issue yet it cant actually be found in the regs.
Re your comment about you cant prove a negative. I get that however if there is no exemption then the full regs would still apply.
If all you have is your memory of a conversation you are going to get screwed in a road side stop & end up with a court appearance. If you are flying close to the wind its better to have the docs in the car that give weight to your case as then most cops would not even ticket you.
I have made packs up for some people / companies to keep in the vehicles to prove compliance with Towing, GTW, Tacho & O licence regulations.
I can find no legal source for imports being exempt. I can find some info re law changes for this after 31st May 1998 for some vehicles but for others the date is in 1968.
Its an interesting topic & will take some time to get to the bottom of it. Even the Hughes Road Traffic Act legal guide has very little in it that is applicable.