I dont see anything wrong with using stock video. It's just the same as using library music. Many local tv stations around the world use istockvideo. What do you think its there for?
It's the risk you take with using that kind of material and there's nothing to stop other broadcasters using it. That's why stock libraries have 'buy out' clauses, so you pay a larger fee but retain exclusive use for so many months.
It then disappears off iStock for that duration so no-one would ever find out your secret or indeed, finding a rival channel use the same graphic in a promotion just to show you up.
You're speaking in the abstract. The reality of this situation is that UTV has no reason to fear any of the things you've described. What's it to them if a few internet geeks find out they copied and pasted their idents? And who's going to use these graphics to "show them up"?
When you're crediting it to your creative team, it is a bit of a cheat.
A cheat? Nobody, except a subset of posters here, cares who creates idents.
All that matters is that these idents are completely fit for UTV's purposes. These look great on screen, they're very Christmassy, and apparently they were cheap as chips. UTV evidently doesn't employ anyone capable of producing stuff like this, so buying a few stock backgrounds is one of the best decisions they've made in a long time branding-wise.