Thanks are due to others for providing a stimulating discussion. Emergence is a tricky concept. It's easy to slide it down a slippery slope, and turn it into something implausible and easily dismissable. But it's not easy to delineate the interesting middle ground in between.
All material properties seem to follow from low-level physical properties.
This, of course, is so ubiquitous a phenomenon that it's not deeply interesting. After all, serious people do like do use the term, and they think they mean something interesting by it. The fact that overloading occurs just around when there are 35 users on the system seems to be an emergent property of the system. Intelligence and many other interesting properties emerge over the course of evolution by genetic recombination, mutation and natural selection. Biological and psychological laws and properties are frequently said not to be reducible to physical laws and properties.