Possible to enqueue scripts and CSS to Multisite Network dashboard?

You can use the global variable $current_screen. It has the property is_network, with a boolean value, that indicates if we are in /wp-admin/network/ or not.

add_action( 'admin_print_scripts', 'network_scripts_wpse_91699' );

function network_scripts_wpse_91699() 
{
    global $current_screen;
    if( !$current_screen->is_network )
        return;

    wp_register_script( 'test', plugins_url( 'test.js', __FILE__) );
    wp_enqueue_script( 'test' );
}

This action hook can also be used like

add_action( 'admin_print_scripts-site-new.php', 'callback' );`

and it will only print in the screen /wp-admin/network/site-new.php, so there’s no need to check if the current screen is a network one or not.