I would like to know if there is any kind of official study with the OD formats used to publish datasets worldwide with respective percentage.
I don't know about worldwide, but for Europe you can find statistics on data formats on the ENGAGE portal.
The Open Knowledge Foundation (OKFN) published a study it did on government data portals around the world. A number of different variables (criteria) were used. I don't recall data formats as one of them, but if not you still might be able to reverse engineer from their study data.