I agree with you about the RFI potential. I was in a meeting and they just dropped it on me that they were going to use Cat 5 ("just like we use in the office"). We won't be going anywhere until there have been extensive EMI/RFI tests, and I sure don't want to get that far and find out there is a problem.
On the other hand, the people who made the suggestion have certainly been around airplanes. Airplane people are funny about RFI. They won't let you operate a laptop during takeoff and landing, but they will let you fill the plane with racks of PCs and monitors, with cables running every which way.
Since I suggested looking for something like shielded Cat 5, I agreed to look into it even though networking is not my thing. I figured you would know if there was such a thing, so I just dropped a note here before calling it a day. Thanks for the help, Rob