Surveys and data are stored in a hierarchical structure. The security groups possesed by a user determines how high in that structure they can go.
Hence if a user has the admin security group then they can create and add themselves to projects. However unless they have the organisation privilege they cannot access projects in a different organisation. The same applies to a user with the organisation privilege. They can create and access different organisations and all the projects within those organisations however they cannot access organisations or projects in a different enterprise.