I flicked over to channel 855 and Five Live was carrying on as usual - in fact they even said, "I hear that if you're watching on TV you've lost pictures at the moment, well we'll try and paper over the gaps for you!". Obviously no-one had told them that it wasn't interactive today so we couldn't hear them anyway!
You'd be amazed how many people watch sport on TV with commentary fom the radio (especially cricket on Channel 4, audio from Radio 4).
Even if 5Live commentary was availiable on the interactive service this would probably have disappeared with the programme
It would be possible for BBC1 to broadcast the sound of 5 Live in such an event, but I don't think that has ever happened