Inspectorsparky, welcome to the forum.
Alot of 'ifs' as to what qualifies as "likely to become energized". I am sure the NFPA could clarify. However- IF a romex runs over a black iron gas pipe or CSST and a big Texas rat chewed on it then yes the gas line is "likely to become energized". We have to presume eventually a rat will invade the attic.
If you believe that a rat will chew on the NM in the attic, then in your opinion is that the NM in the attic will be damaged. Why do you allow the NM in the attic to begin with?
Secondly, why do you believe that a rat will chew on the NM specifically between the NM and the gas pipe, to energize the pipe?
Someone said yesterday 'avoid running romex over or under the gas piping and keep a clearance' and that about sums it up. If I inspect a house and a romex is wrapped around the gas piping I will flag it for non-compliance. Even though there may not be a specific written code it is my job to identify dangers and future potential problems.
Don't you believe you're treading over thin ice with this statement? How would you substantiate the violation if the installer asked for a code reference to back up the red tag?
Have you ever submitted a proposal to amend the NEC to support your position?
"Does the fact that a romex is run under or over a gas pipe mean that it could become energized?" My interpetation as an AHJ is "YES IT DOES."
Are you the AHJ or do you
work for the AHJ?
Remember (and I say this with respect)-when you pass a Journeymans test and satisfy licensing requirements the unwritten responsibility requires you to use common sense. If you stand back at the end of the day and look upon your hard work and something jumps out at you and looks as if it might cause a problem-it probably will. Change it then.
One person's common sense is another's perception of overkill. One person can stand back and look at an installation with pride, where another can walk along behind the installer and find all sorts of things they do not agree with. Where do you draw the line if you do not adhere strictly to the wording of the NEC?
In my limited experience, I have found a plethora of people who take excessive pride in their work yet commit code violations left and right, who believe that their excesses beyond the NEC overshadow their lack of compliance with portions of it.