I have the costco Cathay card as well, when I first applied I applied for a sogo card which was rejected because foreigner.
Applied for the Cathay one at the branch 2 years ago, got rejected, but the lady at the branch had a lot of pull because she called them and gave the rep crap, they said they would reconsider, and a week later the card came in. I honestly think they are more careful when foreigners apply for the costco card since rejected foreigners will complain to costco and disturb the qi.
So yes you can get one but you need to be persistent.
Tom , I applied for the anz card, I've spoke to managers , made formal complaints, but they absolutely will not issue a card to a foreigner without a guarantor. If you press them , they will make another excuse for denying a foreigner.