Where to add track_changes option in migrate_d2d class
It seems you want to synchronize sites.
http://timonweb.com/using-hash-value-trackchanges-to-detect-source-data-changes-in-migrate-for-drupal-7 
If you follow on this example you have mentioned above, Filter nodes by the update time these are changed after you deployed at last. You use MigrateSourceSQL. So you able modify a query.

If you want to synchronize sites, use the module: services or feeds.