Can't speak for every area, but in the times we've done any sort of major work (UPS replacement or building expansion, usually) at our offices, the drawings were all done, reviewed, and stamped by our design/build contractor's engineering consultant, which local inspectors all treated as 'good enough' after what was probably a cursory permit review on their part. The only exception was when we went to our local Caterpillar rep to add generator output breakers, where they drew it up and submitted to the city for thorough review and permitting. I think the inspector's view of it is essentially "The engineer drew 4x250Cu, the customer's there every day so they're gonna see it immediately if you try to cheat by substituting Al or 200, so there's really no need to bother unless we hear about something fishy."
