Hi Adrian,
I haven't seen tasks without execution in jBPM4 yet, maybe you can explain a bit more about how you create your tasks.
It seems like timers (the TimerImpl class) is not possible without an execution since they need an execution to signal or fire an event to.
I use the following code to get the timers for a specific task:
ExecutionImpl execution = taskImpl.getExecution();
List<TimerImpl> timers = session.createCriteria(TimerImpl.class)
.add(Restrictions.eq("execution", execution))
// .add(Restrictions.eq("eventName", "event name here"))
.list();