Yes, but it took a while, I received an initial (automated I am guessing) response acknowledging my complaint fro DoT then probably a week or so after get an email from an actual person essentially saying they would be contacting the airline for an explanation.That was about the same time as my refund email was received.

Re the cc chargeback, I got a tel call from the bank a few days after contacting them and providing background info online, to discuss with me and saying they believed I had a case (I had been promised refund by Air NZ then they renegged, which is what cc were basing their case on) and they also would be contacting airline.