I have found this to the opposite. Around 80% of all my intra European flights I have been upgraded. Maybe this is a OSL thing, but I have found that they easy do it there. Very nice of them.

This summer, my second trip during the busy summer months I was on my may back to ORF via IAD. When I did the checkin in Oslo I asked if the could put me on the waitlist for economy extra. The very nice checkin lady told me I was already on the list for a upgrade due to over booking and asked me if I liked window or idle. I said idle and I got 3 A on both the OSL-CPH and CPH-IAD. That is how SAS are supposed to handle over bookings.