Of course it didn't happen stateside:

Google's auto translate labels the Japanese title as 

"30-car train of "relief train" Yokosuka Line E217 system phenomenal"

What seems to have happened is that a rather long (15 cars) electric commuter train suffered a mechanical failure, and another 15-car set of EMU's was assembled to tow it out of the way, resulting in a train that is probably longer than many of JR's freight trains (You can see the trailing consist has it pantographs retracted). Japanese railfans must have gotten wind of this unusual event, as viewing this on YouTube reveals several related videos of this same train from different photographers, including one where the rescue train is brought to the underground station to couple onto the stalled consist.

---PCJ 

(edit: renamed title for clarity)