Had a similar issue with Comcast. My horrible solution was a Ratshack A/D converter, running the stereo output into that and then into my digital preamp--had huge problems with the threshold trigger on that thing... during low passages, it would stop feeding PCM, which meant my processor had to relock when the quiet passage ended. Better solution was getting an ART DI/O and doing roughly the same thing. Quality from the audio out of my cable box, obviously, wasn't paramount.
Best solution was getting a different CATV box that could be set to PCM output. That is what works for me now...
Best solution was getting a different CATV box that could be set to PCM output. That is what works for me now...