I saw another Nigerian company for which an "exception" had been made. Overall, I think it's risky business right now, especially if you manage to snag a desirable .ng domain. I don't mean this as offensive, but it's not unimaginable in Nigeria that a few greased palms could lead to an "exception" being made for re-assigning your DNS record if you don't have local interests there to back you up.
And likewise I searched the government website and none of its accredited registrars offer straight .ng registration