I believe that they are referring to the microwave pumped incandescent sulfur lamps. These things are really cool, that is to say hot. The bulb is a golf ball sized sealed quartz sphere with some sulfur powder inside. You then pump a LOT of microwave power into it until the sulphur turns to a gas and the plasma lights up. They generate a LOT of light. Too much for a point light source and generally are placed at either end of a long light pipe. The light color is very good too, perfect for growing plants. The problem is that they are unsuitable for smaller venues. They only come in one light level and that is huge. They are also really noisy because of the high pressure air cooling system to keep it from melting, and cooling the magnetron. The bulb is also kept spinning with a motor so that it heats evenly.
Individual lamps are very very expensive. The savings come in the fact that your whole warehouse might only need 4 of them.
I used to have some links to reports about them around here, but they no longer seem to be in my browser. A google search for sulphur microwave light turns up a lot of reading material. like:
"In this new light bulb, sulfur excited by microwaves emits a bright
white light. At the DOE's headquarters, a sulfur bulb at each end of
one 240-foot-long light pipe replaced 240 individual 175-watt
high-intensity lamps. One Tootsie-Pop-size lamp gives off the same
light as more than 250 standard 100 watt incandescent bulbs."