Comment 1 for bug 1479445

This comes from the fact that our BlueZ version still relies on an older API version of ofono as we have implemented. It listens for changes to a "SignalStrength" property on the org.ofono.NetworkRegistration interface which doesn't exist. The propery is named just "Strength" these days. See https://bazaar.launchpad.net/~ubuntu-branches/ubuntu/wily/bluez/wily/view/head:/audio/telephony-ofono.c#L922 and https://github.com/rilmodem/ofono/blob/master/doc/network-api.txt#L127 for more details.