Aluminum plate for EMI shielding
I remember similar approach being done at my workplace few years ago. However, the correct thing to do is weld the plate fully and ensure that the two cable sections are fully isolated. Also you need to use EMI/EMC shielding gaskets along the door if its applicable. 

Since in your case it's a cable tray open to interference, the plate alone won't do it. Ensure that the cables have shields on them and it's grounded correctly.