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What is mva? Oh basically watts?

It's a higher number than the carried power, because AC electricity has those stages when the voltage is smaller than the nominal value. (Unless it's a DC line, then they are the same.)

Surely this would be a DC line, right? AC induces resistance in superconductors because it necessarily induces a changing magnetic field, iirc (or maybe that's only particular types of superconductors).

Edit: Found this, which isn't specific but refers to it as a three-phase transmission cable which implies it is indeed AC http://www.jicable.org/2007/Actes/Session_A3/JIC07_A34.pdf

http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/scbc2.html

AC doesn't directly induce resistance, no. But there's a shared budget of current and magnetic field, and if you blow the budget the wire becomes a normal conductor.

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