In a topic where we were also discussing triggers via Lua callback, Josh mentioned it:
http://leadwerks.com/werkspace/index.php?/topic/1485-more-thingoids/page__view__findpost__p__16270
Josh:
Solids are the way to handle triggers and volumes. They will be exposed soon.
These are better than physics-based triggers because they can be set to call an action either on a collision, or each frame, or when an entity leaves the volume.