This snippet was sent to me from a developer at toon boom to help me get my templates importing properly.
def import_template(template_path):
paste_options = harmony.PasteOptions()
paste_options.color_palette_mode = "LINK_TO_ORIGINAL"
clipboard = project.scene.clipboard
clipboard.paste_template_into_group(str(template_path), 1, "Top", paste_options)