Note that when they talk about the "National Security Authority" (which only Google translated "agency") they actually write in the article "Nasjonal Sikkerhetsmyndighet" (NSM) which is the Norway's security authority:
https://www.nsm.stat.no/ and not the US' NSA. So what we know is:
"No Norwegian authority contacted by (the daily newspaper) Aftenposten said that this equipment belongs to them. Aftenposten has no reason to believe that the Norwegian authorities are behind the transmitters."
The (shorter) article in English as written by Aftenposten:
http://www.aftenposten.no/nyheter/iriks/Secret-surveillance-...