I read the article but didn't understand what the deal actually was. Do they pay no interchange on Citigroup issued Visa cards branded as Costco? Do they pay n

I read the article but didn't understand what the deal actually was. Do they pay no interchange on Citigroup issued Visa cards branded as Costco? Do they pay no interchange on Citigroup issued Visa cards? Do they pay no interchange on Visa cards? Do they pay no scheme fee on Visa cards? Do they pay no fee to their acquirer?