protected IBaselineSet getSnapshotContribution(ITeamRepository teamRepository, IBuildResultHandle buildResultHandle, IProgressMonitor monitor) throws IllegalArgumentException, TeamRepositoryException {
   IBaselineSet baselineSet = null;
   ITeamBuildClient client = (ITeamBuildClient) getTeamRepository().getClientLibrary(ITeamBuildClient.class);
   IBuildResultContribution[] snapshotContribution = client.getBuildResultContributions(buildResultHandle, new String[] { ScmConstants.EXTENDED_DATA_TYPE_ID_BUILD_SNAPSHOT }, monitor);
   if (snapshotContribution.length > 0) {
      IBaselineSetHandle baselineSetHandle = (IBaselineSetHandle) snapshotContribution[0].getExtendedContribution();
      baselineSet = (IBaselineSet) getTeamRepository().itemManager().fetchCompleteItem(baselineSetHandle, IItemManager.REFRESH, monitor);
   }
  return baselineSet;
}

IWorkspaceHandle streamToCheck; // you'd have to retrieve the stream or workspace you care about somehow
IBaselineSet snapshot = getSnapshotContribution(repo, build, monitor); // per the method above.
if (!snapshot.getOwner().sameItemId(streamToCheck) {
// Delete build result or what ever else you need to do.
}