I may be wrong, but I think it's the other way around. The law allows only company-level unionization, but there are ways to get effective sectoral bargaining

I may be wrong, but I think it's the other way around. The law allows only company-level unionization, but there are ways to get effective sectoral bargaining agreements sometimes. In Europe, we have laws that encourage it. For example, Finland has generally applicable collective agreements. If a large representative majority of workers achieve agreement with enterprise representatives in an industry sector, the agreement can become generally applicable. Every employer must observe at least the minimum provisions of a wide national collective agreement once it's considered representative in the relevant sector. (Finland does not have laws about minimum wage. There is very little need for them because generally applicable agreements set the minimums.)