It's usually done in the construction industry by experienced glazers when the only other alternative is replacing large expensive sealed units damaged by welding etc. In a commercial office highrise that can be costly so they will opt to try and see if polishing will appease the architect. I don't think it is offered as a service usually, only an alternative to expedite finalizing their contract!

I have seen good results in some cases, and will get ahold of the company contact I last had it done to see what he has to offer.

Likely the reason city hall told you it could not be "altered" was likely a liability issue, whereas they felt that any alteration to the tempered glass could cause it to loose it's strength. I would say the scratch itself would be more likely to cause a tempered unit to fail than polishing.