[Symbiote]

That's also how the auxiliary content in digital TV works -- the content that isn't video, audio or subtitles.

The channel guide and semi-interactive text content (i.e. "modern" teletext) are special packets in the MPEG stream, and are cached by the receiver.

[izacus]

Yep, and the MPEG streams in Europe still carry actual Teletext on some DVB-T/C streams and even IP-TV.