Is it possible that they just use a LoRa radio? The frequency seems to match and the claimed ranges make me think in that direction.
https://medium.com/@dconrad/how-new-long-range-radios-will-c...
Post by Beep Networks cofounder.
> Our team at Beep Networks is now working with LoRa radios here in San Francisco, and we’re getting signals through at over a mile of range. That’s in the city, through walls, with a tiny battery-powered sensor device — no towers or giant antennas involved. We know folks who are getting 10 miles in every direction when they put these radios on towers in rural areas, where there’s less interference.
[0]: http://www.beepnetworks.com/img/datasheet.pdf
[1]: http://www.digi.com/products/xbee-rf-solutions/rf-modules/xb...