I don't know about the trains but looking at shipping:
-Nordstream 2 has a capacity to transport 55 billion cubic meters per year[1]
-The biggest LNG transport ship "Mozah" built by Samsung Heavy Industries can transport a equivalent of ~162 million cubic meters in a single load
This leads to a ~339,5 full loads per year needed to replace the pipeline volume. Nordstream 2 probably wouldn't run at full capacity initially but even at 50% utilisation it would be nearly impossibe to replace it with shipping.