I’ve always wanted to do this, but Andrew Barton (aka the “Blogging Machine”) beat me to it.  He has written a PowerShell script that will sync user roles (which are not stored in MPs) between management groups.  This is great for when you are trying to keep your pre-production and production environments in sync.

Check out his blog post and grab the script from the Customer and Partner Solutions blog:

http://blogs.technet.com/b/wincat/archive/2013/03/28/copying-user-roles-between-management-servers-in-service-manager-2012.aspx