It seems to me like they do more than just generate QR codes that download a static document. They’ve built out software that helps the visually impaired navigate pedestrian and transit infrastructure. The software seems pretty complex, beyond what a city would likely have the expertise or budget to build from scratch on its own.
QR codes wouldn’t solve this problem, because they would still house a link that has to be opened in the NaviLens app to be of any use.
These codes don’t just take you to some static document. It opens up in the NaviLens app, which when use features like the gps, gyro, and camera in your phone to provide more rich, contextual information.