Auction for Premium or Business Class mileage earning.
 

There should be a simple list by airline that indicates if an auction won changes the class used for mileage accrual (ie 200% VS 5%). It significantly affects how much an auction is worth.

Through trial and failure I have found SAS sends the business class code, but neither Latam nor TAP do. They send the original booking code.

In the USA?
 

What about AA, DL & US?

Not sure about AA and UA but DL it depends when you upgrade.

If you upgrade before T-24, you are typically placed into the revenue PS or F/J fare buckets (typically G for PS and Z for J) and get the mileage bonuses, but if you upgrade within T-24 you are typically placed into the upgrade fare buckets that don't provide additional mileage