This project just provides maps for indoor places. It doesn't do anything special to augment navigation in these places beyond the standard (GPS, WiFi, etc).

When they talk about (augmenting) positioning with Wifi and Cellular data, they are talking about the same stuff they use on the regular Google maps. This data is collected from cell tower info, and the Wifi stuff is sniffed from the Google street-view cars and then augmented by user-data as people with devices come into contact with these devices and send info back to Google.