The first time I heard about this was last week when I was listening to the economic issues that the article mentions on NRK "political quarter" (NRK is the national broadcaster) with the word "waste" being thrown around a lot. This article from VG debates the cost and puts it into contrast what could have been done instead: https://www.vg.no/nyheter/i/q6k3ko/skipstunnelen-er-historis... ... it's been contentious as I understand.
It's also a bit of a farce. The largest party in government (Labour) has repeatedly said no, this is stupid, it's too expensive, it's not worth it. Their junior partners, however, want it. And then one of the "fiscally responsible" opposition parties signaled that they would support the tunnel. So to avoid the junior partners splitting off and agreeing on a budget with the opposition, Labour now supports the tunnel too.
No doubt it will cost a ton and be derided as a boondoggle/used as justification for austerity by the conservative wing which indirectly made it happen.