Article 1.2 of Regulation (EU)548/2014 foresees exemptions for transformers designed for specific purposes. This includes transformers specifically designed for emergency installations, which are exempted. It follows logically that a transformer that is replacing an identical unit designed specifically for an emergency installation is also exempted.
Disclaimer: Please note that the European Commission cannot provide a legally binding interpretation of the EU legislation, as this is the sole competence of the European Court of Justice. Any remarks from the European Commission services are without prejudice to the position the Commission might take should related cases arise in a procedure before the Court of Justice.