The firewire port on my Cox Scientific Atlanta DVR is active, but everything is encrypted. So it seems the law states that they have to have active ports, not anything about being able to actually transport any content over those ports...
I have an Elgato EyeTV Hybrid usb tuner capture device that can get OTA ATSC or Clear QAM cable. It works great and captures a digital stream just as it is broadcasted. In my area, all the OTA and Clear QAM streams are MPEG2, both SD and HD.