MINIMUM distance? I'd say about 3 inches .... the boxes bump into each other.
Otherwise .... I again remind everyone ... section 90 of the NEC makes cleat that the NEC is NOT a design manual, and simply complying with the code could very well result in an inadequate installation. It's a 'safety' code, not a 'use' code.
If I were to design a public building, I'd go look at a vacuum cleaner first. How long is the cord? You might consider that in spacing your receptacles.
For a similar reason, I'd make sure there was a receptacle in every lobby, stair landing, and closet. If the space is divided by a door, or something that suggests traffic through it, I'd consider one on each side of the path.
Ditto for the hall lighting. I've seen far too many code-compliant hallways that were little more than dark tunnels with exit signs at the end. There are ample means to provide for both 'energy savings' AND decent lighting levels.
