AA appears to have changed the rules to close this "loophole". aa.com now states at
http://www.aa.com/i18n/travelInforma...Pass_terms.jsp
"Day passes are not valid for use at the facilities of other airlines with which American Airlines may have reciprocal lounge or club access privileges." so no SIN lounge access if that is true. You must buy a year's AC membership to get QF SIN lounge access.