There are things that can interfere, in particular in a hospital, particularly around the teleradioloy or radiology areas. Many hospitals opt for shielded cabling systems (still generally Category 6), however some still use the unshielded variety. But pay particular attention to where the cable paths are run. This may also be true around dialysis machines and other machines that require higher voltages. No cabling system will work properly or support your applications if it was not installed properly.
As for your plenum question, that depends on whether the return vents are ducted or not. If they are not (which is usually the case) then yes, the cable must be plenum rated. There is also language in the new national electrical code that states that it must be limited combustible cable or those areas must be have sprinklers. Your local inspector can provide you with guidance in this area.
This was first published in January 2006