They could negotiate in bad faith, sure, but that's exactly where the collective bargaining of the union kicks in, and the union has the option of taking action. It exists for just this situation.
But this would be after the collective bargaining and signing a contract laying out the terms for union employees. If non-union employees can get better terms, the union can simply annul the contract and force a re-negotiation where they can't be denied because labor law? Or do you mean they could demand re-negotiations and strike otherwise?
Germany is said to be a lot more pro-labor than the US, but as far as I'm aware, unions can't strike during the duration of their collective bargaining contracts.
Germany is said to be a lot more pro-labor than the US, but as far as I'm aware, unions can't strike during the duration of their collective bargaining contracts.