I've just read an interesting article about how difficult it is today in some countries for DSL and cable operators to compete due to the sheer number of rivals in this sector. True, I can see it in France, for example. In Paris I can choose between at least 10 different DSL providers and the highwater mark for tripple play services (Internet access, unlimited landline calls and IPTV) is 30 euros per month, set-top box included. And competition is getting fiercer with alternative providers such as Free adding service upon service while sticking with the 30 euros per month price tag.
So the only real differentiator you could have against that competition is a wireless 2G/3G network that you bring into the bundle. To stay with the French example, Orange, SFR and Bouygues are going in the direction and are now all offering a DSL and set-top box. For now, I don't see a lot of combined fixed/mobile offers except maybe common billing, which won't make a lot of people switch to another DSL provider. But I suspect that might change in the not so far future when solutions mature to let people access the content stored in their set-top box or in their home network from their mobile device while being away. A unique chance for mobile operators with fixed line assets as they are in the right place to pre-configure the mobile devices and the set-top box (maybe even centrally) of a household to work together seamlessly.
Throw some femtos into the equation or simply a 3G USB modem with a SIM card that automatically installs when you plug it into your notebook. A daily fee or a couple of euros extra a month automatically and transparently put on your monthly invoice. Quite a number of options DSL/cable only players do not have. I am curios which fixed/mobile player will go ahead first to heat up the competition.