If cage or server access was shared between Iron Mountain customers, how can Iron Mountain not have a record of what's in what cage or what's on what server?
If Iron Mountain customers like OSS were free to add or remove things without Iron Mountain's knowledge, then their (OSS's) access would've been limited to cages or servers dedicated to their (OSS's) own clients' data. Allowing an OSS ex-employee the same access they previously would've had should be a non-issue, from Iron Mountain's perspective.