I guess the first "jBPM4" should have been a "jBPM3" in your question.
In jBPM4 the timers are in the JBPM4_JOB table, there is no foreign key to link the entries there to the JBPM4_TASK table so I don't think it is possible to retrieve timers for a specific task. However you can get the timers for an execution or for a process instance since there are fields for that in the JBPM4_TASK table.