I side with the group that says transformers do not require working clearance. The IR scanning makes the issue a bit more difficult, I will agree. But I submit that the act of looking at something does not comprise "examination," in the intended context of the code. In the English language, I concede that the word "examination" could easily apply to the act of looking or photographing an object, with expectation of learning something about the object's condition. But we also speak a second language, that of the technical aspects of our profession. The NEC is written in that second language, and we cannot always use "conversational English" as the means of reading, and interpreting, the NEC. I believe that the word "examination," as used in NEC 110.26, means that the worker's hands are past the covers and there is a tool (e.g., voltmeter) that is touching something internal to the enclosure.
By way of a partial supporting argument to this point of view, allow me to mention that arc flash labels are not required for transformers. And well they should not be. I say that in part because there is nothing inside a transformer's enclosure that should ever be touched while the item is energized, and in part because the software I use to perform arc flash evaluations (SKM) does not know how to calculate the arc flash energy at a transformer (i.e., there no breaker inside the enclosure that could open to terminate an arc flash event).
