According to their own doctrines, no JW knows if another JW is anointed or not and that has to include the GB members.
From the January 2016 Watchtower
Jehovah knows those who belong to him.” Unlike Jehovah, the brothers who count the number of people eating the bread and drinking the wine at the Memorial do not know who truly is anointed. So the number includes those who think that they are anointed but are not. For example, some who used to eat the bread and drink the wine later stopped. Others may have mental or emotional problems and believe that they will rule with Christ in heaven.”
The GB announced that these new GB members are "anointed Christians" however they have no special, God given powers to make that call, only their trust that these men are telling the truth.