With the upcoming opening of the Ueno Tokyo Line, JR East has announced the special trains (rinji ressha) typically running on weekends and holidays, that will utilize this route:
-Ltd. Express Odoriko 161/162 Abiko to Izukyu Shimoda and return, 7 or 10 car 185 series
-Express Burari Yokohama/Kamakura-go Iwaki to Kamakura and return, 7 car 651 series
-Ltd. Express Kinugawa 92/93 Ofuna to Kinugawa Onsen and return, 6 car 253 series
http://news.mynavi.jp/news/2015/01/23/312/