Tagging posts to custom taxonomies using XMLRPC in R

It looks like custom taxonomies aren’t supported by metaWeblog.newPost.

For self-hosted WordPress installs, one could try to use this hook, to adjust the tagging of posts added with metaWeblog.newPost:

/**
 * Fires after a new post has been successfully created via the XML-RPC MovableType API.
 *
 * @since 3.4.0
 *
 * @param int   $post_ID ID of the new post.
 * @param array $args    An array of arguments to create the new post.
 */
 do_action( 'xmlrpc_call_success_mw_newPost', $post_ID, $args );