An automation is a piece of work plus a schedule. "Every Monday at 9, check for supplier price changes since last week and summarize what moved" is an automation. It does exactly what it would do if you asked for it by hand, on the day and time you picked.
Automations only ever see what the person who set them up can see. If that person loses access to something, the automation loses it too — at the moment it runs, not the moment it was created.