In our part of the world braking systems need to be type approved with the towing vehicle. Otherwise, a retrofitted electric brake device on the towing vehicle would require an IVA, which is a bit of a hassle for the owner. Things aren’t made any easier by the fact that there is no industry standard for electric braking systems to which all car manufacturers can work (to my knowledge at least not for trailers under 3500kg). Without standardised ex-works provisions it would be impossible to swap tow cars or trailers.
Maybe things are a bit easier in Australia and a towcar with a retrofitted electric trailer braking system doesn’t have to be type approved.