The only available hook for reordering is
hook_nodequeue_swap($sqid, $nid). looking at the code, this hook is only called from
nodequeue_queue_swap is itself only called from
nodequeue_queue_down. Any other way to reorder a subqueue (ie.
nodequeue_save_subqueue_order) will not trigger any reordering hook.
This means a module can ot plug itslef into the reordering of subqueue like it can for node addition and removal.
We need this feature for one of our project (we need to track changes in queues) and I'm willing to work on a patch for this. Calling
hook_nodequeue_swap() mutliple times for each nodes in a reordered subqueue seems inneficient. I plan to add an additional
hook_nodequeue_reorder($sqid) triggered after completion of any reordering operation.