This is probably based on the idea of Cobalt bombs (https://en.wikipedia.org/wiki/Cobalt_bomb https://en.wikipedia.org/wiki/Cobalt_bomb) intended to make areas

This is probably based on the idea of Cobalt bombs (https://en.wikipedia.org/wiki/Cobalt_bomb https://en.wikipedia.org/wiki/Cobalt_bomb) intended to make areas uninhabitable due to radiation. But in that case the Cobalt 59 is placed directly around the nuclear bomb, and spread across the area by the explosion. It doesn't seem plausible to me that this would be a real danger. If I'm close enough to a nuclear explosion that can affect the Cobalt-59 in my car, I'm probably vaporized anyway.