> Scale it down? Seems pretty obvious to me. If you can make it happen in one city, you have a foothold.
It doesn't work scaled down, though. (I'd argue that it's a bug in existing policy voting and adoption frameworks that it can be enacted when scaled up, but that's a different argument.)
You can't sensibly enact a policy like this if it draws its funds from the taxes of people who aren't within the city in question (and it would be horribly unjust if you could). So you're talking about paying for a basic income within a city by adding a substantial tax to the residents of that city. That would result in a substantial motivation for any mobile business or person to relocate (and higher-income people are often more mobile), and for any new business to set up shop elsewhere.
Cities are small enough that it's entirely possible to relocate if your local government becomes too obtrusive. A policy like this only "works" if you have a scale large enough that the majority of people opposed to the policy are nonetheless forced into it by virtue of finding it less awful than moving.
The burden of moving to a new country is high enough to deter it for all but the most egregious issues; the degree of bad policy required to motivate leaving a country is far higher than the degree of bad policy required to motivate leaving a city or even a state. As a result, the average person will likely find themselves far less aligned with the policies of their country than their city or state.