I have seen these requests come in and be met. if it was a reputable consultancy then the HR function will have made the interviewers deliver their written feedback and will pass that on - whether or not it gets sanitised along the way, who can tell, though again I have seen unsanitised feedback delivered and result in some lively discussion.... you can also ask for any handwritten notes, though good luck getting them. I doubt they'll claim to have lost all records - that would give them legal exposure.