I may be misunderstanding, but here goes. The Account Migration Tool white paper says that some user types won't be migrated when using the tool:
Built in system users
I took unlicensed accounts to mean any users that were not assigned a Named User License. I just ran this tool and it brought all repo users (except for the ADMIN account which was excluded), including users that did not have a license. I expected those to be left behind.
Can someone please help clarify this for me, as I assumed otherwise.