In the UK (or any other country with data protection laws): a Subject Access Request will get you all interview notes and internal emails, the company has no choice in the matter.
Doesn't this law mean that companies will go to great lengths to avoid generating anything that can be tracked or demanded? All decisions verbal, etc...?
most employers keep written records to avoid any possibility of a discrimination suit.
the government has very strong guidelines on this sort of thing, and if you're a large company with an HR department, the Information Commissioner is likely to not believe you if you state that you don't keep written records about job applicants, and destroying the information is a criminal offence.