Long-hault superconcucting transmission line will still face inductive and capacitive losses, no freebie there. Maybe supercapacitors combined with superconductors? Ah well, one can always dream!
Superconductors do saturate at a point, and can only carry so much current, but because there's no resistance, voltage drop and transmission efficiency is not a limiting factor. Transmission line efficiency will jump to nearly 100%.
The problem with superconductors is that even "high temperature" superconductors still need to be cooled by liquid nitrogen. (They're high temperature only when compared to those other superconductors that need cooled with liquid helium.) Sounds like the wires they're using here still need to be held at temperatures that would freeze liquid nitrogen, though.
The cooling is rather counter-intuitive; it's not to cool heat generated by the cable, as electrical resistance is so close to 0 that no heat is generated. (Superconducting wires would not require thermal derating for raceway fill.)
