In today's Helsingin Sanomat saying that you can upgrade your summer special prices for 99 €/one way. Unfortunately, you only get the AY Plus points for the original booking class. In this respect it seems to be an inferior offer compared with the upgrades offered by Swiss, British Airways and the recent offer from Blue1.
But, still an interesting novel approach.
I was unable to find any instructions in the
www.finnair.com.
Update: I just read the ad more carefully. Upgrades are only available through the telephone service.