I answered some questions on SO, they were migrated when meta was launched, I later created an account on meta and associated it with my SO account. I (as in my meta identity) then became the owner of those answers, as normal.
However when I disassociated the accounts, my ownership of those answers stuck, and they are still associated with my meta account, even though I haven't touched those posts since they were moved to meta.
I would expect that my revisions to migrated questions and answers would show up under my username from the original site, grayed out, similar to what happens when the original poster has deleted their account.
status-bydesign
. At least that's how I would implement it.