The Guardian recently carried an article referencing the EU’s desire for the European Court of Justice to play a role in the arbitration of disputes over the Channel Tunnel, notwithstanding the EU’s abandonment of its previous insistence that the ECJ should have oversight in other areas. Yet there are simply no grounds for the ECJ to interfere. The Tunnel was built under the bilateral treaty of Canterbury (1986) between the UK and France, and any problems can be resolved through ordinary bilateral procedures. Disputes are matters of international law, without the need for any specifically EU involvement. More generally, rail and transit conventions between the UK and EU member states operate internationally, and in terms of Brexit legislation have thus been the easier topics to deal with.
The Eu is looking to involve the ECJ in arbitrating disputes over the Channel Tunnel, but there’s no need for the court’s involvement.