It's called electro coating, it's a general term nothing specific, it's used for paints, (both liquid and powder) and actually quiet a wide variety of other types of coatings. The only reason for the electrification is to cause more product to be attracted to the target rather than dispersed into the air, it also causes the coating to be very uniform because the coating itself electrically isolates the substrate so the charged paint is attracted to non-exposed portions. For things like powder the static charges applied actually keep the particles in place until the items goes through an oven for final curing (where the powder becomes liquid and flows)
It could have been a form of plasma deposition coating, but for office equipment I'm not sure they'd go to such a degree =) If you want to see some crazy stuff try to find some video of a plasma coating deposit gun in action, the coolest way to paint EVER, and it's cutting edge technology because of the incredible array of materials that can be applied.