Yes, you only have to put the 'actorId' in the Map of variables of the process instance using the varName you want, for example 'ASSIGN_TO_VAR_NAME', then you can use org.jbpm.identity.assignment.ExpressionAssignmentHandler to assign tasks to the actor:
<task-node name="..."> <task name="..."> <assignment expression="variable(ASSIGN_TO_VAR_NAME)" /> </task> ... </task-node>