No, I don't think they've closed HAX. I worked with the system years ago, so I guess that's where the past tense comes from. To my knowledge, it's still being used as a high resolution near Earth SOI (space object identification) sensor. I'm not certain if NASA is still funding HAX for orbital debris studies or not. It was still being built when I got out of the Air Force in 1992. From what I've heard, it's a good system.

From a SOI perspective, it has higher resolution than Haystack and is available more often. Haystack is a dual mode system with an interchangeable electronics set. Most of the time, it's a radiotelescope. When they change the electronics, it becomes a near Earth or deep space SOI sensor. Back in 1992, Haystack was only available for somewhere around 6 weeks each year for the SOI mission. HAX has much greater availability but can't reach deep space.

If you go to this PDF file, it discusses Haystack and HAX on pages 14 and 15. The picture of the Haystack Radar on page 14 shows the electronics package being swapped. One package is lowered from the center-rear of the dish via cables and the other package is hoisted into position.