Hi @lipcsey,
The Fathom-X Homeplug communication will work over any pair of conductors- twisted, untwisted, coaxial, copper, or otherwise. Homeplug was actually originally designed to work over un-shielded and untwisted household electrical wiring.
How far it will be able to communicate over that cable with usable bandwidth is another matter. The presence of twisting, shielding, as well as the impedance, capacitance, and frequency response of the cable/conductors will all affect this.
In any cable, the bandwidth will decrease as length increases, and the rate of decrease may accelerate or there may be a sudden drop in bandwidth past a certain point. This is completely dependent on the above factors and the interactions between them.
-Adam