This is the solution from Peter Baylies (Plugin Author)
add_filter( 'option_aioseop_options', 'itdge_sitemap_addl_pages' );
function itdge_sitemap_addl_pages( $option ) {
if ( !empty( $option )
&& !empty( $option['modules'] )
&& !empty( $option['modules']['aiosp_sitemap_options'])
) {
$my_sitemap_entries = Array(
'/test1' => Array( 'prio' => '0.1', 'freq' => 'daily', 'mod' => '2014-04-01' ),
'/test2' => Array( 'prio' => '0.3', 'freq' => 'weekly', 'mod' => '2014-03-02' )
);
if ( empty( $option['modules']['aiosp_sitemap_options']['aiosp_sitemap_addl_pages'] ) ) {
$option['modules']['aiosp_sitemap_options']['aiosp_sitemap_addl_pages'] = Array();
}
foreach( $my_sitemap_entries as $k => $v ) {
$option['modules']['aiosp_sitemap_options']['aiosp_sitemap_addl_pages'][$k] = $v;
}
}
return $option;
}