Ah yes, interesting question.
1. The cars were all imported as dedicated race cars and hence not subject to tax and can never be complied for road use.
2, The bits that you can see on the outside can be fitted to any stock JCW S eg the rear wing, diffuser and front lip. Would cost all up less than $4k to do and totally road legal. Stickers are $2.6k through MINI but you can get copies for around $70
And finally:
3. if it was a genuine with the killer exhaust, roll cage etc, then the rules are different in every state. In SA I have to swap out some items like the brake lines and take off the wing, diffuser etc, and fit a second seat, road tyres, narrower wheels etc etc and get my rally licence then I can apply to get it registered as a dedicated rally car.
Best thing to do if you have one already is to speak to your local CAMS office and they can hook you up, otherwise but aftermarket copies and make it look like one on the outside