I guess rule 3 is quite clear. if a company is legitimately authorized to take goods (for example) it's no more "steal". Can even happen cases where players agree to share same factory (example), both delivering primary cargo and taking goods. But the player that delivered 1st must agree, since by right are their goods.
but there's a thin line between what you described and what can be considered illegal abusing. For example: 1 company giving secondary production to other company gives an unfair advantage, compared to the other companies, correct?
That's why we like more this solution: Don't take secondary/tertiary cargos made by other companies. That's why we prefer that players respect strictly our rule #3.