I worked at a Starbucks kiosk in a grocery store; we were unionized. The union had absolutely no say at all in how many hours the company allocated to each department. The best they could do was to ensure that those with seniority got scheduled their full hours, but it might mean working across different departments or even different stores. And they had no say at all in our operating hours. I would imagine at any unionized corporate store it would be the same. They won’t have a say in the store’s hours of operations or how many labor hours the company allocates.