First off a couple of things to clarify... I'm not sure whether you're talking about a TiVo or a V6 so...
The ITV Hub app is only available on the V6 and queries about content on there should be directed at ITV as it's their app. VM just provide the means of accessing it via the V6.
If you're talking about the (ITV-Hub branded) CatchUp programs, these are usually available within a day of broadcast but quite often a lot sooner. You can access CatchUp in different ways though, and if you're going via the CatchUp menu - this doesn't always seem to update as quickly as the reverse EPG does.
Subtitles have never been available on any OnDemand programs as long as I can remember.
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Live shows always take longer to appear on catchup than recorded shows. Subtitles are available on most of the apps now, I think that may be why Virgin provide access to them. I don't know why there are no subtitles on Catchup, I assume it is not technically possible. Don't forget if you record a show it will also record the subtitles.
BBC iplayer is the only app integrated with Catchup. When you select a BBC show on Catchup it automatically launches the BBC iplayer app, however it was very slow to load on older Tivo boxes which is why you get more apps on V6 boxes. There was lots of complaints when BBC iplayer first appeared on Tivo as it was slower than when it worked the same way as other channels on Catchup.