Although it's a fun format, I'm afraid this idea isn't really that new at all. As early at 1991, 2CR in Bournemouth did something similar with a radio car - though in that case the listeners were encouraged to go and find the presenter.
Registering the intellectual rights to a "Treasure Hunt" on the radio would be a hugely costly affair. In any case, the BBC itself is not allowed to sell formats in this way - it would have to be via BBC Worldwide. Siphoning off any profit back to Local Radio would be nigh on impossible.