Tokyo Electric Power Company has announced that there will be no 
blackouts on April 2, 3 and 4 (Sat-Mon).  Most railways in the Tokyo 
area will be running at 80% to 100% of their normal weekend levels April 
2 and 3.

Most operators have announced outlines of revised timetables (if not the 
actual timetables) for April 4 onward.  Express services and through 
services to subway lines will be restored in most cases and rush hour 
frequency will be back to 100%

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Narita Express will start running April 4, but not all runs.

On the other hand, Keisei has announced that some Skyliner runs will be 
canceled from April 4.  (No runs will be canceled April 2 and 3)

Keisei Cityliner is not running and won't resume on April 4.

Details here:
http://www46.atwiki.jp/earthquakeinfo_en/pages/15.html (Tohoku area)

http://www46.atwiki.jp/earthquakeinfo_en/pages/40.html
      (Tokyo area including Narita Airport)