After the page is created and you have its ID, and before you restore_current_blog() you do this:
update_post_meta( $page_id, '_wp_page_template', 'your-template-file.php' );
After the page is created and you have its ID, and before you restore_current_blog() you do this:
update_post_meta( $page_id, '_wp_page_template', 'your-template-file.php' );