According to the Decision of the Member States of 8 April 1965, Article 9 states:

“Sont, en outre, installés à Luxembourg les services suivants de la Commission:

• l’Office statistique et le service de la mécanographie;
• les services d’hygiène et de sécurité du travail de la Communauté économique européenne et de la Communauté européenne du charbon et de l’acier;
• la direction générale de la diffusion des connaissances, la direction de la protection sanitaire, la direction du contrôle de sécurité de la Communauté européenne de l’énergie atomique, ainsi que l’infrastructure administrative et technique appropriée.”

I believe this article is still in force, or was confirmed in Edinburgh in 1992.

This means that the CPE requires to be built within the Luxembourg City boundary as it is part of the Commission services, unlike the school.

I cannot see how this could be open to discussion or sudden reinterpretation after all these years. Nor would one expect the Commission, as guardian of the treaties, to attempt to find ways to circumvent it. Surely the other affected institutions such as the Court of Justice, even in its capacity as an employer, would insist that the Commission and the Luxembourg authorities respect the fixed and firm arrangements.

So how is it possible to build the CPE in Bertrange if all parties have already formally committed to Luxembourg-Ville?