I’m assuming you’re talking about this piece of maintenance code right here:
http://core.trac.wordpress.org/browser/tags/3.3.1/wp-admin/includes/post.php#L419
Indeed, the code calls on lower level functionality of $wpdb, which doesn’t contain too many hooks, only one in fact, query.
http://core.trac.wordpress.org/browser/tags/3.3.1/wp-includes/wp-db.php#L1061
So, in order to return an empty result set you’ll have to come up with a no-operation type of query, here are some examples:
SELECT NULL;(returns 1 NULL result)DO 0;SET @ignore_me = 0;SELECT * FROM `$wpdb->posts` WHERE 1=0;