You are absolutely correct in that they would have no control but it is not to say they will not share in security information as the administrators of these ports.
Additionally, as administrators, they have complete access to all manifests of cargo entering and leaving these ports, Just think how valuable information of military supply movements would be to our enemies.
Think about delays of these shipments that can be caused by the administrators of these ports.
Just think about the fact that at most 5% of cargo undergoes inspection and how easy it would be for a port administrator to manipulate or overlook "questionable" shipments and not make their presence known to our security people.
As for having confidence in Homeland Security, just think of the aftermath of Katrina and the person (Chertoff) who couldn't find his a** with both hands, running it. While you're at it, ask him how he and his boss, President Bush, are coming along on securing our borders.
Do you mean like the manifest of military supplies that go to support our troops in Iraq and Afghanistan? Those same military supplies that are currently going through Dubai and...DP World?
Or do you mean secrets that they couldn't already obtain from the commercial port operations they already have in the U.S. or the commercial port operations the Saudis already have in the U.S.?