That is a great question. As we all know DC is no longer. I had a reservation using that code, but, went with the code for EC and cancelled the DC one, for $ 8.88 difference, it was not worth the chance that they would refuse the rate with the DC code.
I have been told if the online reservation site accepts it they will honor it ( I was told by the station mgr. at MCO), but, I simply did not want to take the chance.