There are emission on the wall lights, and only 1 light in the scene. The lighting is extremely basic. It uses the same input setup as a model material - single light position. However there are three lighting modifiers that can be applied for specular strength, reflection strength, and ambient levels. These can be ‘tweaked’ to modify the overall look. This is very simple though. Thats why its simplepbr 
Its so many default resource and render setups can be supported without modification.
Oh. side note… I didnt try an envmap on the scene. hrm. Let me try.