How does the lucky attribute affect IVs during trading?

I started playing at launch but dropped off for a while as new features were rolling out. As such, I have a bunch of 2016 Pokémon but no lucky Pokémon, until I did my first trade recently. Based on how I understand trading these old Pokémon should work, I have a reasonable expectation of getting some lucky Pokémon back as well.

But what I don't completely understand is how a Pokémon being lucky affects their new IV values. Are the new values generated based on a higher stat floor? Do the current IVs prior to the trade and turning lucky play a role? Could a Pokémon with high IVs actually have lower IVs after turning lucky? I essentially just need to understand this system better so I can better target what Pokémon I want in return during trades. What's the current understanding for stat rerolls when a Pokémon being traded turns lucky?

According to this and this Reddit thread there is a IV floor for lucky Pokemon being 12/12/12. This overrules the friendship level IV floor effects and, similar to friendship trades, prior IV doesn't matter.

This gives a strategic advantage to those with less than 10 lucky Pokemon trading July/Aug 2016 Pokemon as they are guaranteed to be lucky and, with the IV floor, have great IVs.