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If they Waymo service area overlaps with the city limits at all, that's good enough.
If only a minority of people have access, it will resolved based on whether any of them got this access by luck or signing up early, rather than by being Waymo employees, journalists, or famous.
If the cars arrive with Waymo employees in them, or even in the driver seats, the answer resolves Yes if i can find any credible evidence of 1 trip where it's plausible the car was doing more than half of the driving work. If it's hard to find evidence of any such trips, it'll resolve No.
When Waymo launches somewhere, that answer will resolve Yes. If they suspend service etc, it will still stay a Yes.
I might well bet on this question.
Similar question where the deadline is 6 months sooner: https://manifold.markets/BoltonBailey/which-cities-will-have-waymo-one-se