If I am not wrong, other than listing the device mode on the Manage Devices page, getting the notification for the backhaul failover is not natively supported by XIQ or HiveOS/IQE.
Maybe you can look into using XAPI. Device Mode should be included in an XAPI call like below.
See below for the details.
The other possibility is to setup the syslog and process the log for the backhaul failover according to your needs.
I haven't really looked into the SNMP trap for this, but I think it's not supported either.