I'm not sure where they're getting their figures, but I have yet to see anyone reading an eBook, let alone a eManga, on their cell phones here. Been here for about a year now and when people see my eReader, they say it's pretty cool but they haven't seen anything like it around. I know the Librie was launched here a few years ago, but it didn't take off too well due to poor marketing and a fubar DRM scheme for their books. Secondly, the Japanese love to read, but they also like to trade-in their previously read books (used book stores are huge here). Not sure where this would leave eBooks in this culture; i.e., cannot take them to a used book store for credit, etc.
That's a lot of money they're talking about, but I have yet to actually see anyone using them. FYI I live in Tokyo and take the train regularly (that's pretty much how people get around here), plus I visit Akihabara frequently, which is essentially the tech-mecca of Japan, not a peep. Hopefully this is a ploy to get people interested in e-content and check to see what all the buzz is about.
BTW Thanks for the link to Anime News Network, lots of cool info there to check out!