Thank you Ralph for your comment. As per the javadocs, the above only provides the permitted actions for the "logged in user". However I am looking for all the permissions assigned to each role in a Project and to all the users in it. I worked it out by extracting the process configuration source and reading the XML to find all the information I needed. Roles>PermissionIds>ActionIds. However I had to keep create a separate mapping file to store the relation of the permission/action Ids and their names.

IContentManager icm = teamRepository.contentManager();
Map pd = projectArea.getProcessData();
projectContent = (IContent) pd.get(ProcessContentKeys.PROCESS_SPECIFICATION_KEY);   
teamContent = (IContent) pd.get(ProcessContentKeys.PROCESS_CUSTOMIZATION_KEY);
ByteArrayOutputStream stream = new ByteArrayOutputStream();
icm.retrieveContent(<team/project_content>, stream, null);   
String contentString = new String(stream.toByteArray(), content.getCharacterEncoding());