That's cool indeed to know. I seemed to notice some kind of similar pattern on Kintetsu trains as well. Kintetsu however does seem to have differences in having either the left or right (or both) lower headlamps on. Does anyone know more on this?
Interesting topic.
I didn't know the indicator of Hankyu / Kintetsu.
By investigation, I found that almost of railroads company uses two pettern(ON/OFF) indication.
Only Nankai ,
Local service : ON(Left side only)
other service: ON (both side)
If you want to know about other company,
please read this by google-translation
http://ja.wikipedia.org/wiki/%E9%80%9A%E9%81%8E%E6%A8%99%E8%AD%98%E7%81%AFThe lamps you thought as tail-lamp may be the indicator.