EclipseLink has an open feature request to allow a better way of allowing an admin server to access multi tenant data: https://bugs.eclipse.org/bugs/show_bug.cgi?id=355458 - vote for it if it is important to you.
The way around it would be to create a separate persistence unit for your admin console. One way to go about this would be to move the multitenant metadata to an EclipseLink orm.xml file, and use it in your tenant persitence units, while the admin persistence unit just use the entity classes. You might want a field in the entities that can be mapped to the tenant column that the admin console could use and query against, but be read-only or inaccessible to the tenant specific persistence units.