I created a wiki family using the following test settings:
http://rafb.net/p/JICuAZ14.html
Then I tried to merge the only accounts (one default bureaucrat account on each wiki which is created upon installation of MediaWiki) which had the same username on both wikis. I ran migratePass0.php, but it only added "one" of the accounts (that on my enwiki) to centralauth database (localnames table).
It seems like migratePass0.php has to be run for each and every wiki in the wiki family once. There is no standard way to do this though.
Version: unspecified
Severity: enhancement