I had just read the FT article and was about to post the URL, when I saw that Stoop had already done so. As I read it, this article indicates that friends and family who stay at no cost, do not need to be notified and the property does not need to be registered. However,if the property had been advertised in any way previously, the owner still needs to register and declare that it will not be let commercially in the future.
This sort of makes sense and would certainly cause less grief for the friend and family only owners but does seem to veer away from this being a question of national security and becomes more of a tax collection issue.
This all seems to be a transient situation, so where do we go for the definitive article?