Get all possible values for Planned for attribute when creating a new work item?

URI projectAreaUri = ...
IProcessClientService processClient = (IProcessClientService) repository.getClientLibrary(IProcessClientService.class);
IAuditableClient auditableClient = (IAuditableClient) repository.getClientLibrary(IAuditableClient.class);
IProjectArea projectArea = (IProjectArea) processClient.findProcessArea(projectAreaUri, null, null);
IDevelopmentLineHandle[] developmentLineHandles = projectArea.getDevelopmentLines();
for(IDevelopmentLineHandle developmentLineHandle : developmentLineHandles) {
	IDevelopmentLine developmentLine = auditableClient.resolveAuditable(developmentLineHandle, ItemProfile.DEVELOPMENT_LINE_DEFAULT, null);
	for(IIterationHandle iterationHandles : developmentLine.getIterations()) {
		IIteration iteration = auditableClient.resolveAuditable(iterationHandles, ItemProfile.ITERATION_DEFAULT, null);
		System.out.println(iteration.getName());
	}
}