Sr. Oliveira, habude na linha rs
STSADM -migrateuser copia as permissões de um usuário para outro, mas na mesma site collection. Mais detalhes:
http://www.toddklindt.com/blog/Lists/Posts/Post.aspx?ID=75
Opção 1: De grátis = SPUserUtil
http://blogs.msdn.com/b/krichie/archive/2005/04/08/406729.aspx
Cloning
Cloning allows you to “Clone” one users set of permissions for other users.
For example, a user joins an Authoring group for a specific portal.
All these users share the same set of roles, yet they are permissioned individually on the sites and areas.
Cross Site Groups are probably the best mechanism to support this, but the need to do this across site collections is still a daunting task.
With cloning, this is now easy.
UPDATE: essa ferramenta é antiga e foi "abandonada", consegui baixar daqui:
http://www.techhead.co.uk/sharepoint-portal-server-2003-sps2003-migrating-users-and-more-spuserutilzip
Talvez o MetaVis abaixo seja melhor...
Opção 2: MetaVis Migrator
One of MetaVis for SharePoint
features often overlooked by its users is embedded SharePoint site security manager. Site security manager allows to browse and copy site permission levels, permissions, groups and users between SharePoint security groups, sites, site collections
and even SharePoint farms, view site permissions inheritance status, break it or restore it – all in an intuitive Windows Explorer style user interface. Ref:
http://sparchitect.wordpress.com/2010/05/13/manage-sharepoint-site-security-permission-levels-permissions-security-groups-and-users-with-metavis/
Opção 3: Desenvolver uma custom application para essa finalidade...
Abraço!
Half Abude Scheidl