Unfortunately, it's more complicated than that. Those exported JSONs contain enough information to visualize a city (including changes made by the warp tool) but not enough to keep it editable. In your case it would mean that you would be able to import your "warped" city, but not to warp it further after that. It wouldn't be much more than a slightly adjustable image. Actual saving and loading a city is a large task and for this reason it is not implemented yet.