It's not that far removed from the old 56k modems. The main difference is that VDSL uses multiple carriers at different frequencies, but each individual carrier bears some resemblance to a 56k modem. VDSL is basically 10000 old skool modems running in parallel. It's no coincidence that the VDSL tone spacing is about 4kHz, or the bandwidth of a phone line. Your "voice phone line" is just carrier #0.

Also VDSL uses some very sophisticated channel modelling, whereby it measures the coupling between your copper wire and all the other copper wires in a bundle of telephone wires and cancels the interference out. This allows it to send carriers down the wire at frequencies that were previously unusable. It's basically a beefed up version of the 56k training, taking advantage of today's computers running faster and being able to run a more complex channel model/estimator in real time.

As a whole the VDSL signal is mostly on ultrasonic carriers, but it would be possible to tune into one of the carriers and listen to it. (Interesting project anyone?)