All the examples in the photos are clearly lit, so the idea that these won't use power or will be unlit doesn't seem plausible. Just think of how many paper ads are lit from behind, when you're walking around a mall or airport.

Second, the contrast is bad. Most colors wind up looking washed out. It can be nice for reading, but advertisers want their ads to pop.

I don't see this taking off for advertising at all, because advertisers won't like it. What it does seem more useful for is informational signage. Building directories, maps, etc. Because those don't need to be lit, and the e-ink can be a lot higher resolution than a lot of jumbo LED displays.