For some reason that train-to-train song comes to mind when I see this:
「トレイン to トレイン」 http://www.youtube.com/watch?v=LJ9vkt7BHYI

edit: It turns out the title of the pixiv is 「鉄道詩ぃちゃん」, which translates to "Railway Shii-chan". Damn I'm good!

edit 2: Aaand I completely forgot to explain myself. Train-to-train is a song sung by/about Tetsudou Musume, Railway Attendants, that work at train stations in Japan. The outfit Shion is wearing here is confirmed to be a Railway Attendant uniform by the title of the pixiv. But we don't have a tag for that, and it's sorta military-like, right?

So why is Shion wearing a Railway Attendant uniform? Well, the pixiv artist writes:

気が付いたら前回の投稿が2ヶ月前とかそんな馬鹿な……そしてまたしても誕生日絵！マイピクで鉄ちゃんなやなぎんさんへ、2月23日お誕生日おめでとうございます！名鉄制服な詩音描いてみましたけど細かいところ分からなくていい加減です／(＾o＾)＼　あと制服が男性用なのは私の趣味です　■コレ好き→http://www.nicovideo.jp/watch/sm4233726　　□3/1付けでRR160 位！？（　 Д ）　ﾟ　ﾟ　ありがとうございます！

I realised my last post was 2 months ago, and that sucks... So here's another birthday drawing! I chose a rail-girl for Yanagin-san, happy birthday on Feb 23rd! I tried to draw Shion in a Meitetsu uniform but I might have half-assed the details. ／(＾o＾)＼　Also, I prefer the men's uniform.　- I like this → http://www.nicovideo.jp/watch/sm4233726 - on Mar 1st RR160 rank!? （　 Д ）　ﾟ　ﾟ　Thank you！

I had hoped to find something useful in the artist's comments, but all I really found was the nico video. Apparently Japan Rail played a part of one of the songs from Higurashi as a boarding signal at a station where they wear this uniform.