Unsalvaged salvage debris is not owned by the cargo department, but salvaging debris as other roles just because you have a hardsuit may be considered powergaming depending on circumstances. IC conflicts can arise from others interfering with the savage techs by salvaging debris for personal use or for other departments.
Items within the cargo department, including any salvage wings, can be treated as other items in other departments are. Stealing a crate that cargo intends to sell from inside cargo can generally be treated similarly to someone stealing a crate of materials from engineering.
Items which salvagers have left outside of the station are not the same as items within the department. It is much more reasonable for someone to consider an item that is in space outside of salvage as “abandoned”, even if that is rarely the case. Taking these items can still result in IC conflicts. Unlike taking items directly from the salvage debris, taking these items can be treated as stealing from a person or from the department, but not to the same degree as stealing directly from a person or items within the department.