The Deutsche Bahn ... is the national railway company of Germany, and a state-owned enterprise under the control of the German government. Headquartered in the Bahntower in Berlin...
SNCF French for "National Society of the French Railways") is France's national state-owned railway company.
These German/French state enterprises are basically buying in into our privatised sector. It's a commercial matter. But, nationalising our railway network by the UK government was not allowed under EU laws. Unfair advantage as in subsidising our (to be) state enterprise. Recall this from the discussion at the time since that was a pretty good reason for leaving the EU.