Looking at current efforts and strategies for implementing the Once-Only-Principle OOP/OOTS versus former Cross-Border CroB Principles in EU E-Government regulation/projects like SDG/TOOP/mGov4EU, we analyze these developments concerning the HEI/EDU integration, also looking at the different states and (central/de- central) structures in some EU Member States as well cross-border, where already digital services and standards are used, like EMREX/ELMO and EWP. Against this background, we make proposals for some improvements for interoperability for OOTS and CroB implementations for HEI/EDU with standards and security.