Have you tried to use knowledge base to get processes and then cast it to NodeContainer?
Collection<Process> processes = kbase.getProcesses();
for (Process p : processes) {
NodeContainer container = (NodeContainer) p;
// following line should return all nodes in the process - hopefully
container.getNodes();
}
NOTE: It is written by hand the code so it can have some typos... don't have access to my development environment now so was not able to verify that.
HTH