Hi Alexandra,
I don't think there is an automated method, if that is what you are asking. Our college is introducing Alfresco as our main repository, and we would expect that staff would begin to migrate their old legacy files over to Alfresco and re-link them over time.
For the time being, at least the legacy files are there and nothing is broken. The good thing is that people can't add more files to legacy going forward, so the problem can't get worse.
I hope this is somehow helpful to you.
Regards,
Michael