I have been in both ports of Barentsburg and Longyearby and I can confirm that I saw no mines or nets. I can't vouch for the rest of the place, its a damn big ocean
Oh and if them flattops give you too much trouble then just sink them on your first run at the convoy. Then you get a free ride all the way to Liverpool if you do not run out of ells first
I sunk two of them my last time around a Bogue and a Casablanca class.
Oh and watch out for Icebergs!