We found a Macintosh-only solution from Palomar Software. PLOTTERgeist is a Chooser-selected driver for plotters connected to a network via Shiva's NetSerial product. You could work around the no-PC limitation by connecting the plotter to an A/B switchbox connected to the NetSerial on one port and a peripheral-sharing switchbox (Black Box has them) on the other.
For contact information, search the Technical Info library under "Black Box."