We were discussing this very thing today
we were discussing if it was actually in the CAA's remit as it being a none flyer ground based and all, we decided it wasn't all the way up to it becoming airborne which threw up some interesting thoughts as how could the CAA legislate on anything to do with fast taxying for anything else, after all they are no longer registered as aircraft, and if it never gets airborne then it is not in their sphere of influence, it's more in the Dept of Transports as its a ground based vehicle.
If they say well it flew, does that mean everytime you see a rally car airborne over a hillock that the CAA should become involved?? or an F1 Car as that has wings both front and rear....... odd situation is it not?