is it a hardware issue?
I'd be curious to know if tivo hardware can withstand 24/7 operation when the temperature hits the mid-40's in the summer.
Unlike a data-centre, you won't leave your a/c going at home just to keep your tivo cool. The other issue is that most channels have a "catch-up" tv service, which is the cloud version of tivo. It's tough to sell expensive and dedicated hardware into that environment. Until recently they were helped by the typical Oz ludicrous retail prices - $1000 for a dual-tuner pvr. That sort of pricing is changing.
I've run mythtv and you just have to accept that the hardware dies after 2-3 years. I just upgrade my desktop and use my old desktop to mythtv duty at that point.
It will be interesting to see if the BOB/BOB2 hardware from the ISPs can hold up in the heat. Even my voip router had problems in the summer. Perhaps it won't matter, with rental payments covering the hardware replacement costs.
I'd like to see more common systems certified to 45-50 degrees for harsher climates. They don't need to be high-power, but they do need to be always-on home-server and media-server type systems. My guess would be laptop-type components with big heat-sinks and large fans in a desktop case. Perhaps even normal desktop systems which are under-clocked to prevent over-heating, or better yet, dynamically clocked systems which just slow down in the heat.