My Grandfather was there in the trenches on the German side during WW1 when this incident happened over Christmas. He remembered the soldiers crossing the lines. He said the words "Can you imagine" this happening during the war when so many men were being killed at an alarming rate. When he looked back on the war years later, he said it was a strange thing to have happen.
With regards to war in general after fighting 4 years in the German trenches he said, "Niemals wieder". Translated that means "Never again" (would he fight).........and said war is crazy.