Past experience can be used to drive good estimation. But it takes experience with the process of estimating to know when you "know" that your experience is relevant, and when it's not clear if the previous experience translates.
We have third parties building portions of our systems and for some of them I can estimate reasonably well their actual net duration because I've had a lot of experience with them, and they've been fairly consistent.
But there are others where there's a wide range, so I think it boils down to whether you can spot a pattern or not.