Triggering the start of a task from a CRON job
Everything you need to manage tasks is in the TasksService, so you should be able to just use that in your controller action to kick off any pending tasks, using something along the lines of:

if (!craft()-&gt;tasks-&gt;isTaskRunning())
{
    $task = craft()-&gt;tasks-&gt;getNextPendingTask();

    if ($task)
    {
        craft()-&gt;tasks-&gt;runPendingTasks();
    }
}


If you have a look around craft/app/services/TasksService.php you'll see you can also grab and run tasks by type which might be useful in this situation.