Yes that’s how the traditional phone system works, single pair from your house back to the exchange (via a jumper block in a cabinet nearby). Modern DSL equipment can get upto 50mbit aggregate speed over 1km of traditional phone wire (so 40/10, or 30/20 or however you would want to set it up)
Condition of the wire will effect it of course, aluminium wire, ground conditions, cross talk etc could lower your speed.
I think the difference with this product is the transceivers are $150 each and you don't need anything else to use them except for a couple of power supplies.
I do find it interesting that their box diagram claims a 2km range.
One catch is that ISPs rolling out VDSL, such as CenturyLink, are often using pair bonding. So despite a typical performance limit of 40/10, CL offers 80/20 in VDSL markets by taking advantage of the fact that homes are typically wired for two lines.
Condition of the wire will effect it of course, aluminium wire, ground conditions, cross talk etc could lower your speed.