I have the hdhomerun quad tuner for OTA ATSC and the other channels come from IPTV. I use TS Doctor to cut commercials but I never see a subtitle or teletext option. Just a video and audio stream.
There will be closed captioning in US broadcasts but there is no separate stream or pid they are part of the video stream, they are often called line 21 captions.
You will need to be sure TS Doctor isn't removing them
Yeah, the US broadcasts will include them. As Martin said, they're part of the video stream. Are you post-processing the file? ie, transcoding or utilities that are clipping recordings etc.