Hey Japan wants to join. I know we are a bit far away but we can form some sort of a tri-something axis.

I think, the joke about Germany and Italy should team up is a reference to the new CEO of Deutsche Bahn, Evelyn Palla, who is from Italy. The "to make the trains run on time" gives a hint here, because this is her declared task.

Not about Germany, Italy, and Japan, forming some sort of axis, I guess.

Japan wants the trains to run on time too!

The tri partners have a mutual goal.

I heard that Japan's trains cannot compete with the Germany's trains. /s