Iron Mountain isn't doing anything particularly special. They just store your big boxes of reports in hopefully a secure area. Show more love to your librarian IMO. Its up to them to tell Iron Mountain that they need box number 0324-233 because it contains the TPS reports from 1972 that you wanted.

We use Iron Mountain to store huge amounts of tape and paper documents along with a daily courier box. The previous incarnation of the offsite storage company before they got bought out by Iron Mountain had much better service. I can't remember what the last bill was like but it was several thousand GBP each month just on tape storage. Document storage is handled by another department and probably even worse due to physical size.