Ok here is my code to grab a package_id of another package within the same subsite. It is extremely ugly.
# Retrieve package_id of organizations package
set node_id [site_node::get_node_id_from_object_id -object_id [ad_conn subsite_id]]
set node [site_node::get_children -node_id $node_id -package_key organizations]
array set organization_node [site_node::get -url $node]
set organization_package_id [site_node::get_object_id -node_id $organization_node(node_id)]
