edit: just noticed I posted in 2018 further up about my experiences back then. Seems things have changed for the positive since then

I’m EBD and routinely fly ORD-ARN-ORD and ORD-CPH-ORD with flights that continue on to other Scandinavian and European cities.

I usually get courtesy upgrades from PE to business when departing from CPH or ARN (west bound, usually on a Friday or Saturday) for the last 3-4 years. I never count on them, so if I want extra space or need more lie-flat time, I will usually buy/redeem an upgrade. But I would say that I have gotten courtesy upgrades ~40% of my flights, and almost all westbound. I’ll go over my past flight schedule and courtesy upgrade emails and try to be a bit more quantitative.

Last summer (July IIRC), my wife and I were flying on separate bookings - I had a EB redeemed ticket in PE and she had a cash ticket in economy. Our PNR’s were separate but linked in the reservation system, and we miraculously both received courtesy upgrades to business in CPH-ORD.

However, I’ve paid cash for upgrades from PE to business on a few of my last 3-4 round trips, and I did not get courtesy upgrades on westbound returns. Not sure if this is coincidence or related to the previous comments about courtesy upgrades as a way to drum up future revenues (I.e., give you a taste of the good stuff, and when you buy it with cash they accomplished their mission?)?

Sometimes it seems that it’s related to PE being full, sometimes it’s not. I haven’t quite figured out a pattern.

The most recent courtesy upgrade was in March 2023. Emails usually arrive 3-4 hours before departure. Here is an example:

You've been upgraded to SAS BUSINESS

We know you spend a lot of time traveling with us and we appreciate it. To show you just how much, we're offering you a free upgrade to SAS BUSINESS when you travel from Copenhagen to Chicago, IL, 17 Mar 2023. This means you'll enjoy extra benefits that make your trip even more comfortable (read more here). And this offer applies to you and your traveling companion in the same booking. Enjoy!

Best wishes,

SAS EUROBONUS

So some anecdotal evidence that courtesy upgrades still happen, but not quite sure about rhyme/reason. Hope that was helpful.