Can I use B-Fi connected speakers, alongside Sonos speakers?

You could use these two systems separately, with their respective apps, and separately through Airplay. Sonos speakers are not able to be integrated into a B-Fi system, though. The Audioengine Connect App is only able to recognize B-FI connected audio systems, and the Sonos App will not recognize B-Fi wireless music streamers. So there wouldn’t be a way to group them together.