Do multiple promotions from the same user group really work?

[WetWired]

As I was investigating adding some promotion capabilities to my activity hack, I found that all promotions are started by the query

$promotions = $DB_site->query("
	SELECT user.joindate, user.userid, user.membergroupids, user.posts, user.reputation,
		user.usergroupid, user.displaygroupid, user.customtitle, user.username,
		userpromotion.joinusergroupid, userpromotion.reputation AS jumpreputation, userpromotion.posts AS jumpposts,
		userpromotion.date AS jumpdate, userpromotion.type, userpromotion.strategy,
		usergroup.title, usergroup.usertitle AS ug_usertitle
	FROM " . TABLE_PREFIX . "user AS user
	LEFT JOIN " . TABLE_PREFIX . "userpromotion AS userpromotion ON (user.usergroupid = userpromotion.usergroupid)
	LEFT JOIN " . TABLE_PREFIX . "usergroup AS usergroup ON (userpromotion.joinusergroupid = usergroup.usergroupid)
	" . iif(VB_AREA != 'AdminCP', "WHERE user.lastactivity >= " . (TIMENOW - $nextrun))
);

and that there doesn't seem to be another comparable query in the system. If I read this query right, when it left joins user and userpromotion on usergroupid, the result will always be either 0 or 1 sets of userpromotion data for that user. If there were, say, both a promotion promotion and a demotion promotion from the same group, where is that handled?