That happens all the time. Utilities always go much further into their overload ratings than we do. I remember seeing (3) 2,500A Switchboards fed from a vault that (when I looked inside) only had a single transformer in it.
That is also pretty common in residential. They put a 50 KVA pole pig on 3 "all electric" homes with 200a panels. I understand most of the time they are still loafing along but there are times I am surprised that they are not smoking. Take a cool Christmas eve, oven going, 2 or 3 burners going on the cook top every light in the house on plus outdoor lighting, hot water and 15kw heat strips going in the air handlers ... times 3
Hi guys Been AWOL for a bit. Our POCO does not allow any reduced neutrals; no way; all conductors must be full size. They also 'may' have an issue with 6x6" conduits; next time I talk with my POCO inspector, I'll run it by.
I can't say I've seen anything larger than 4", except for HV