Post #1849: :
Blender 2.80:
tag = "MyTag"; has_enabled_menus = len([m for m in prefs().pie_menus if tag in m.tag and m.enabled]) > 0; operator(L, "pme.pm_enable_by_tag", text=tag, icon='CHECKBOX_HLT' if has_enabled_menus else 'CHECKBOX_DEHLT', depress=has_enabled_menus, enable=not has_enabled_menus, tag=tag)
Blender 2.79/2.80:
tag = "MyTag"; has_enabled_menus = len([m for m in prefs().pie_menus if tag in m.tag and m.enabled]) > 0; operator(L, "pme.pm_enable_by_tag", text=tag, icon='CHECKBOX_HLT' if has_enabled_menus else 'CHECKBOX_DEHLT', enable=not has_enabled_menus, tag=tag)