What happens if my company makes changes without telling us in advance?

That’s a real concern. Often, companies act without informing workers early, which leaves unions only a margin of reaction instead of preparation. This is why unions push for anticipation - so they can know what’s coming, speak up, and protect jobs before decisions are made. Employers defend themselves by claiming that business interests are hurt if they anticipate change because their market competitors may take advantage. Such a clash of interests is to be expected in the long history of capital-labour relations but unions cannot abdicate from their role of, at least, protecting income for their members, including when employers hide information that may push their members to settle for less or actually lose their jobs.