Just spoke with someone actively involved in the Umba tourism scene about the feasibility of getting an official permit for foreigners to visit the area. Was told that success in obtaining such is so extremely rare as not to be worth trying.
In all probability the same applies to other “no foreigner access” areas.
The consequences of being caught there without the permit is a fine and termination of your Russian visa, and denial of visa application for several years. And the police are said to be happy to charge trespassers.