drush rsync among sites
In Drush 6 and earlier, the rsync command did make some attempt to operate on site alias lists; however, we recently decided that this feature was not useful enough to continue to maintain it, so we removed it from Drush 7.  Truthfully, I'm not even sure that it's working right in Drush 6 -- casual tests showed inconsistent results.

Therefore, the best way to do this would be to just call drush rsync once for every destination site.  You could do this with a simple script.

#!bin/bash
for site in $(drush sa @setA --format=csv --fields=name)
do 
    if [ "$site" != "site1" ]
    then 
        drush --yes rsync @site1 "@$site"
    fi 
done