When you say they are copy-once, does that allow your Ceton/MythTV setup to view the channel? Are you using MythTV or Windows Media Center?
I went ahead and pulled the trigger on the Ceton card and set it up (being well aware of the risks) and note that only a smattering (read: hit or miss) of HD channels (and even SD) come up. All locals come in, Food NetworkHD, TruTVHD and perhaps a few others. I have some "good" email addresses for Buckeye so I may inquire if it would be possible to have the CCI set to 0x00 (copy freely) and allow me to watch/record what I'm paying for.
I used to hook up to a STB via Firewire and it worked fine with MythTV (any channel could be recorded) but it monopolized the cable box, which is why I went with the Ceton.
If you'd like to email me privately, let me know.