From Valve Developer Community
info_lighting is an internal point entity available in all Source games. It can be used to change the lighting origin of a prop_static or a vehicle prop. Set the prop's lightingorigin keyvalue to point at this entity to make the prop light as if it was at the info_lighting's origin. Good for prop_static entities that are embedded in world geometry (like rocks/windows/etc). It also changes the cubemap origin, meaning the prop will show reflections from the closest cubemap to the info_lighting entity. For a prop_dynamic, use info_target.
Note:This is an internal entity. When the map is compiled by VBSP it is processed and then removed: it does not exist when the map is running.
.VMF that has a prop_static using 2 lights (on/off green/red using triggers)
Interlopers Topic http://www.interlopers.net/forum/viewtopic.php?f=2&t=23112