The German initiative KOALA (in English, Building Consortial Open Access Solutions) is a bottom-up initiative that negotiates funding for Diamond Open Access by cutting into library budgets. By pooling resources from more than a hundred research libraries across Germany, KOALA has so far secured funding for ten peer-reviewed journals and two book series.
More details, including a transcript of the entire episode, can be found at doi.org/10.7557/19.7561.