They already have the HD transmitter. All they need to do is operate in MA3 mode. And they are definitely interested in doing this. https://www.radioworld.com/tech-and-gear/digital-radio/takeaways-from-the-am-digital-order
But why now, with so few HD-capable radios in use, especially outside the car, and with no sign that a production/distribution/retail sales push is coming, nor any sort of promotional push that will get consumers talking about whatever product is available?