ManagedObjectReference history = srmPortType.getHistory(
  ManagedObjectReference _this,
  ManagedObjectReference plan);

Where ManagedObjectReference _this = _recoveryRef;
where _recoveryRef can be taken from:
  SrmServiceInstanceContent content = _srmPortType.retrieveContent(_svcRef);
ManagedObjectReference _recoveryRef = content.getRecovery();