Japan Post Japan Today: Japan News and Discussion For 11/30 (no direct link by day) The post already uses pretty small kei trucks. The electric car is only a little smaller for cargo space I bet.
Following is the press release of Japan Post in Japanese only. http://www.post.japanpost.jp/whats_new/2008/1125_01_c01.pdf (sorry I have no time to translate it in English now.) Ken@Japan