So a very long way from "zero emission" then, depending on where its power comes from.

I guess if you stretch the definition rules sufficiently my 25-year-old 4.6 litre V8 4x4 is a "Negative-Emission Vehicle" because it actively reduces the amount of toxic pollution in the air, when you take it down some of the more polluted roads. Drive it in a bus lane and the exhaust gases are cleaner than the air it's sucking in - it's warm carbon dioxide and water vapour, with all the HC, CO and particulates stripped out.

You can imagine a worst-case scenario for the electricity used to charge the cars, or you can imagine a best-case scenario.

The car itself is zero-emission by the definition posted. You are hypothesizing that the electricity used to charge the car comes from a dirty source, but that has nothing to do with the car itself, and in Texas for example, it's easily to choose a "100% renewable" energy provider. I just checked PowerToChoose[0] and found 26 "100% Renewable" plans available from companies like CleanSky[1].

0. https://powertochoose.org/en-us

1. https://cleanskyenergy.com

It's the same in Scotland. Right now the whole country is powered by 100% renewable energy but everything is priced based on all power being generated in and for London from natural gas, because we have to prop up England's failed capitalist experiment.

...as opposed to the communists that delivered you wind energy?