Hi @vaibs,
as the process engine supports expressions in the calledElement, you can indeed call different processes in a multiinstance call activity.
Here is a test method for the expressions: https://github.com/camunda/camunda-bpm-platform/blob/master/engine/src/test/java/org/camunda/bpm/engine/test/bpmn/callactivity/CallActivityTest.java#L132-L160 using this process model: https://github.com/camunda/camunda-bpm-platform/blob/master/engine/src/test/resources/org/camunda/bpm/engine/test/bpmn/callactivity/CallActivity.testCallSimpleSubProcessWithExpressions.bpmn20.xml
Hope this helps, Ingo