Seems unaware of multisite/multinetwork

Attempting to move from an old single install into a multisite/multinetwork installation, all media imports fail instantly. The apache log on the old site shows no attempts by the new server to download data unless wget is used by hand.

My php skills are scant to nil, but I believe the trouble is in this section:

// get placeholder file in the upload dir with a unique, sanitized filename
		$upload = wp_upload_bits( $file_name, 0, '', $post['upload_date'] );
		if ( $upload['error'] )
			return new WP_Error( 'upload_dir_error', $upload['error'] );

		// fetch the remote url and write it to the placeholder file
		$headers = wp_get_http( $url, $upload['file'] );

My presumption is that the upload path is not valid, yet there’s no error being returned other than “Failed to import media… Remote server did not respond” (with debug on).

However I’m not sure whether the problem is in wordpress-importer itself or whether multinetwork needs to patch the functions file in order to return a path.