N's Pokémon have a set nature and have IVs of 30 in each stat. They are incapable of being Shiny.
All of N's Pokémon have maximum friendship when captured; they are the only Pokémon in the game for which this is the case.
So yes, all of his Pokemon (if they have his ID number, 00002, they are his, so that includes Zekrom/Reshiram) are IV and Nature locked. Surprisingly, they have max friendship when caught, too.