The Department 56 product line is rather extensive, but there are items they don’t produce and likely never will. If you want to complete your village with other items, or use Department 56 in other settings, such as a train layout, then scale might matter to you—and “Department 56 scale” is undefined. Here’s how to make sure the things you want to use together will go together, size-wise.
The answer, by Department 56’s own admission, is that it varies. But since I see the question come up again and again, I’m going to tackle it. It varies, but there’s a method to it the madness.