I agree with you that there's no direct zero-sum connection between public transport investment and self-driving cars but I'd say that's missing the point.

This is a tangent, but there aren't two separate pots of currency labelled 'PRIVATE FUNDS' and 'PUBLIC FUNDS' in society. Nor does private industry have a monopoly on R&D. As you acknowledge, it's entirely feasible through political action to change society's declared priorities, and there's nothing 'full communism' about it: Private companies operate within the market defined and backed by the state and legal system.

Self-driving cars, even if ready to go tomorrow, present a worse value proposition than public transport unless we enter into the realms of a post-scarcity society. My opinion is that it's a shame that the current sociopolitical system has ended up offering better incentives by having half a dozen mega-corps pump endless amounts of money into their own proprietary research of something less useful to society than public transport, which provides similar functionality.

Is it a useful, actionable statement? No, of course not! We're wasting time on HN not debating in parliament ;-)