OPC 30000 describes in chapter 10.2 an access to server specific object types which is mandatory. For that matter the folder CtrlTypes is defined in the specification document. A proper definition of the concerned node is not part of the PLCopen information model, neither in the NodeSet nor somewhere in the document.

I would assume this folder node to be defined also within the PLCopen information model (NodeSet) thus having a well known NodeId. Otherwise each vendor defines this node on their own forcing the clients to rely solely on the browse path to said node.