Circuits off of different phases in close proximity.

When I do a network upgrade of a school, there has to be a dual data and 2x dual power outlets for every computer position. Normally there are existing data and power so I just replace the cat5 with cat6 leave the power and add another power beside it. When adding the power I run a new circuit and that circuit feeds 2 classrooms which equals 6 dual outlets, theyre labelled what phase they come off and the breaker number. I do this so the Certificate of Compliance only covers the work we do and we arent held responsible for other peoples work which is usually of a low standard in the schools and its quicker than identifying and the existing circuits which I would then have to do a earth loop impedence test on and have to label every outlet.

The inspector from the PM company not electrical inspector but an electrician said we had created a hazard because there was now 415 volts potential between 2 outlets 50mm apart. I said if it was that much of an issue then outlets wouldnt be put within reach of children in schools in any case.

What are your guys thoughts on this? Is there a code reference from the NEC that addresses this not that it is applicable to me Im just interested.