That's not to say that Murdoch couldn't bring out a "Sky+2" for instance, that was indeed a TiVo.
All he'd need to do would be to take the US DirecTV TiVo (series 2) as the model. It would basically be a UK-ised series 2 TiVo with a Sky tuner (CAM) and could use a version of the Tribune EPG data delivered via a spare channel when the TiVo wasn't recording anything. I believe the DirecTV box does just this.
Of course, whether he'd want to do so would ultimately depend on how much he could increase the "premium" subscription to Sky to cover the costs - and how many existing Sky+ users could be persuaded to up their monthly fee by "just another £2" to get the new box.