Optiontown allows SK an additional revenue stream where a flight is oversold in a certain lower cabin class. The customer pays to be at the front of the op-up queue. Upgrades with miles are an additional revenue stream where a flight is undersold in a certain higher cabin class.
The only overlap would be in the case of oversold lower cabin class, undersold premium classes. In this case I would assume Optiontown to take preference as the revenue generated to SK is clearly significantly higher. I doubt there will be much risk that one pays double for the same upgrade. These op-ups are manually handled by revenue management and they would have a certain order of priority.
(Of course this is from my armchair CEO position. Who knows what SK would do)
I asked customer service, using the chat function on SAS' webpage. The operator checked with EuroBonus, and I was told that the collaboration with OptionTown would continue. It would be possible to request upgrades using both OT and points, but that OT "probably" would have preference.
The requirement for 117-stock was confirmed, leaving OT and standby-upgrade at gate (probably having close to zero availability henceforth!) the only way to upgrade itineraries ticketed on other airlines.