Broadband is very much a natural monopoly, like electricity or water.ATT used to say that the phone network was "a natural monopoly". Today we'd laugh at that. Really, this example is so glaring that I'm surprised you'd offer this argument. And in fact you acknowledge that the local loop is separate from the actual network. But the difference in the US is that this is a free market -- I can choose to use Embarq (the traditional copper-wire circuit-switched carrier), or I can (and do) use Vonage, or scads of other IP-based carriers, or I could do like many people do and just use cellular. We the consumers are getting to choose just how this unbundling happens.
If, for some reason, you think that there's something sacred about telephone, while data is different (or vice versa), there are other counterexamples as well.
In New York, while electrical transmission remains a monopoly, generation has many choices. It works just like the phones: where the infrastructure demands a single source, that's what we get, but that doesn't mean that the people that provide the wires can be the only one involved in the business. (I pay more for electricity that's generated in part by windmills)
And most obviously, it seems to me that most people have access to two broadband carriers, albeit their capacity varies widely (but that's what markets are all about, right?). Virtually everyone I know has a choice of a DSL provider or a Cable provider.