A good source of information and some guidance documents can be found at the Scientific Archivists Group web site www.sag.org

Was the “Medical Imaging Service Provider” contracted to scan all the trial documentation following completion and not actually involved in the conduct of the trial?

If the images are of trial documents presumably the original documents/data/information are with the people who generated that data (e.g. the investigator).. If the documents/data/images include such things as; the Investigator site files; and/or any patient records or information that could identify they, then the sponsor should not receive these records. It is difficult to be any more specific without more information.
There is also information on clinical archiving at www.therqa.com.