Wanting to update... We just flew EVA Air to Taiwan and took a side trip to Hong Kong on Dragonair. EVA to Taiwan and return on Economy Elite allowed us to use the CARES harness for our 1 and 3 year old. We did purchase seats for both. Dragonair wanted to provide us with the baby belt extender but we told them we brought our own safety harness... all in my terrible Mandarin. FA on Dragonair was confused but Dragonair and its parent company Cathay specifically state on their websites that as long as you purchase a seat for your child you may use CARES or car seat. We mentioned this and they were fine. Both flights had ample open seats so I am fairly sure they would have allowed the infant a seat even without a purchased ticket.