Closed Captioning is in the analog VBI. However in ATSC it isn't necessarily linked to clock or TVGOS.
One of our local analog cable channels (not a host channel) switched from analog origin to modulation of the corresponding ATSC subchannel. In the process Closed Captioning was eliminated entirely, and is still missing to this day. I'm sure that will be the future.
What's more, not only is the source digital subchannel of such poor quality OTA it's all but unwatchable, the analog cable retransmission is even worse. Perhaps it doesn't matter if there is CC or not because even ordinary people are complaining about how nasty it looks. The prior analog feed wasn't great, but watchable.
I can imagine the FCC requiring feed through of Closed Caption data in such cases, but of course as far as the cable company is concerned today, they probably think they are simply helping to push people to digital box rental.
Even if such forwarding of ATSC Closed Captioning to analog modulation was a requirement, TVGOS would still be a separate issue. It would additionally need to be intercepted and piped through for our purposes. You can argue it's EPG data for the public, but it's also *advertising* media paid for by TVGOS so that perhaps complicates the notion of mandatory inclusion.
Of course in some cases TVGOS may be willing to pay for it as they do with host channels.