How about: The editor must pull all data from OSM (like no AI generated stuff and other imports) and push all data to OSM. With explicit user consent the editor can additionally push data under OSM-Licence to other services. It will make sure that all data gets transmitted to OSM and allow additional publishing to others.
So the editor must always push all changes back to the OSM-DB (in your case of abandoned railways no changes, nothing to push) and if the user agrees it would be ok to push the data to a third party (in your case the user could agree, that he wants to push that data under ODbL to OHM). Afterwards the railway could be deleted and this change will be pushed to OSM.