I think we should move now the creation of voicecall driver to ril_radio_state_changed(), making this call when powered on. I see the following traces in maguro on boot:

...
Jan  7 09:52:18 ubuntu-phablet ofonod[1446]: [UNSOL]< UNSOL_RIL_CONNECTED
Jan  7 09:52:18 ubuntu-phablet ofonod[1446]: We are polling CLCC and received an error
Jan  7 09:52:18 ubuntu-phablet ofonod[1446]: All bets are off for call management
Jan  7 09:52:18 ubuntu-phablet ofonod[1446]: ril_radio_state_changed: state: ON ril->ofono_online: 1
...

Although calls work in the end, we probably can avoid receiving an error from RIL when requesting it the current calls if we do that after changing to power on state.