Just throwing out a suggestion, not sure if its a neat approach.
sharedProp_1.addEventListener(CollectionNodeEvent.SYNCHRONIZATION_CHANGE, listener1)
batonProp_1.addEventListener(CollectionNodeEvent.SYNCHRONIZATION_CHANGE, listener2)
protected function listener1(evt: CollectionNodeEvent) {
tempFunc();
}
protected function listener2(evt: CollectionNodeEvent) {
tempFunc();
}
protected function tempFunc() {
if (sharedProp_1.isSynchronized && batonProp_1.isSynchronized) {
//Do soemthing
}
}