Admittedly it's been a while since I have had U-Verse, but I was able to disable wifi on the modem, put the modem in "DMZ mode," and make an Apple Airport Extreme work well with it. Still not real bridged mode, although the router behind the U-Verse modem in DMZ mode would get the real external IP address handed to it so it doesn't act like a double-NAT situation.
You still had to have your TVs run through to the actual U-Verse modem, though, and can't plug them into a router sitting behind it.
The trick is enabling IGMP proxy. The first 10 seconds of a Uverse TV stream is transmitted over UDP. After 10 seconds, it switches to multicast. You need IGMP proxy on the PFSense box (or IGMP proxy capable switch) to relay that multicast traffic to the ports on the other interface.
After that, DMZ your PFSense box, add just a few firewall allow rules, and you're done!
It's how they deliver instant channel change. The unicast udp burst is about 30% higher than the nominal bitrate of the multicast. The STB stitches the unicast and multicast together seamlessly.
My U-Verse provided box has my Airport Time Capsule connected via Ethernet and it's MAC put in the DMZ. From there, the Airport is my network gateway. It was a little bit of a challenge to setup, but is possible.
