Five seconds on Google pointed me to the AA web page
http://www.aa.com/content/uk/travelI..._airport.jhtml
which says the following:
Park Avenue:
At London Heathrow, Park AvenueSM is an innovative personal check-in service, exclusive to First and Business Class passengers and AAdvantageŽ elite-status members.
So it is for
all elites, regardless of status level or class of services.