Security folk are well aware that low value government agencies are targetted by spies, not for the information they hold, but for possible conduits to higher value agencies (the government is all connected after all).

I think you are right and wrong - right that Norway in itself uninteresting, but wrong that it doesn't present a valuable target for spies. Like you said they are hooked into the EU - what better way to get insight into the machinations of the EU than a government that is probably awash with chatter about sensitive EU matters, but that erects little defences against spying thinking noone could be interested in little old Norway.

I wouldn't be surprised if those cell towers included ones that were run by the US and Russia (maybe China too).