Well, this facility is trying to improve their electrical safety and risk so questions are being asked about long standing practices/issues/concerns.
I had thought this would be the correct place to ask this question with all of the experience and diversity here but out of 5 answers only one was serious, valid and helpful. I would have thought that responsible, serious, helpful responses would have been more than 20%.
Good Heavens - put the knives away and lighten up. It's okay to take the job seriously, just take yourself lightly. The 80% just told you they didn't know where to suggest to look.
What you are asking about is dead freaking normal through the industry. You might find a housekeeping OSHA regulation. It is not an NEC issue, and likely never will be.
If the change made in the first draft report for the 2020 NEC makes it through the process, the following will be added to the end of 450.9
Transformer top surfaces that are horizontal and readily accessible shall be marked to prohibit storage.
Interestingly, even this won't make housekeeping an NEC issue. Once the sign gets painted on the transformer, and the inspector is satisfied, that is the end of it. No electrical inspector is going to check back and make sure the house is clean. OSHA might have a fit, the NEC won't.
I personally don't think stacking stuff on top of a transformer is inherently dangerous. However, I have heard of a bunch of research showing the sloppy workplace have increased accidents. And that makes it worth while to generally cleanup - not just the tops of the transformers.
Best I could suggest is to read up on a 1000 pages of OSHA regs - unless it is 2000 pages. And it likely won't be in the electrical section.
However, I suspect the answer is to find a manager with ovaries to step up and say, "We are cleaning this place up. Every day, pickup your work area. Friday afternoon pick up, put away, mop. Everybody is on deck. Areas are assigned." Roll it out slow as a safety issue.
A couple of my clients do this. Works well. Only two issues I've seen:
At the start, older journeymen aren't interested - they want the kids to do it. "You're going to pay me to mop." Uhhh, yeah, that's what I said - unless you are telling me you can't do it.
Management has to schedule time every day for cleaning. Outrageous Example: You got 8 guys and girls. And you want an hour of cleanup every day. You have to hire another person to makeup the 8 hours. What manager is going to suggest that? No, it isn't that bad, but the point is true. If management wants the place cleaned up - they have to pay the bill.
As for the poor responses, Internet advise is worth what you paid for it. Except for mine. It's worth somewhat less.
the worm