Targeting Cisco QoS over multiple remote links on AT&T Switched Ethernet Fiber

I'm working on creating/cleaning QoS policies for voice at my place of work but have run into a question on how to best accomplish what I'm trying to do. First off, we have about a dozen remote locations that are all connected via AT&T utilizing their Switched Ethernet Fiber product (Layer 2 connectivity). AT&T has a Ciena at our HQ and all remote locations. Most remote locations are connected with a 50Mbit link, some of the smaller locations at 10Mbit. Our link at the HQ is a 500Mbit link. I'm modeling after Cisco's AutoQoS. Normally I'd leave in the AutoQoS entries which classifies voice and control correctly, and provides 33% and 5% bandwidth respectively. But since I'm sending data over one single higher-bandwidth link at the HQ, these default rules do not work as we never hit the 500Mbit bandwidth statement, so QoS never is triggered. However, we are saturating some of the remote 50Mbit links at times which has generated complaints of voice not working properly.

I'm looking for a good way to set up QoS most effectively on the HQ router and though't I'd ask the hive mind. Right now my thought was to create 3 class maps per location that match-all on network ACLs and data class (voice, control, data) - following the Cisco AutoQoS. Then I'd have one big policy map that contains all 36 (12x3) classes with appropriate bandwidth statements. That won't work though as I mentioned earlier that we never hit the 500Mbit on the HQ router.

How can I get the one AT&T facing interface on our HQ router to recognize that traffic heading to one subnet should be accounted for separately as a lower-bandwidth link? For example, if traffic heading to 192.168.78.0/24 has surpassed the 50Mbit, start policing or shaping.

For good measure, here is a chunk of how I originally was thinking of setting things up:

class-map match-all Loc3Voice match access-group name Loc3VoiceSubnet match class-map voice class-map match-all Loc3Control match access-group name Loc3VoiceSubnet match class-map control class-map match-all Loc3Default match access-group name Loc3DataSubnets !Total BW to Loc3 = 50Mbit / 51200kbps policy-map AllRemotes class Loc3Voice bandwidth 16000 class Loc3Control bandwitdh 5000 class default fair-queue ... Repeat above 3 classes for all other locations