I think that Simon was referring to the imagesetters used to make the negs. They are not amateur level gear (especially price-wise) but have been used for decades in large printing shops, so the experience in using them is in the same sort of business. The input to the imagesetter is typically Postscript driven, so all the usual manipulations you could imagine, and more, may have been used to end up with the perfect neg for the final prints.

I'm not sure of the precise relation of the RGB separations to the Pt-Pn print either, possibly the adjusted separations are then contact-printed to one master-neg for use on the print?