I don't think that running your own router fully solves this issue. I've had this disabled from day 1 of having fiber and running pfSense behind the BWG320. I also have a backup TMobile connection. When the the ATT line goes down (like when the fiber is disconnected...or cut) my DNS won't resolve and just goes to the ATT DNS hijack. For failover to actually work I have to unplug the BGW320. I have posted on ATT forums and pfSense and nobody knows how to bypass this.