Compatible.
http://www.tp-link.com/en/article/?id=406
Q: Are 500Mbps PLC adapters compatible with 200Mbps PLC adapters? Are TP-LINK PLC adapters compatible with adapters of other Brands？
A: 500Mbps PLC adapters also accord with HomePlug AV Standard, so they are compatible with 200Mbps adapters, however the powerline rate will drop to 200Mbps. The adapters accord with the same standard should be compatible with each other.