Interesting that radio is finally paying some attention to their HD channels.
A couple of years back, a station I worked with had an interesting experience. The main channel was in HD and due to a technical issue the HD1 channel had no audio. Analog was working fine but no audio on the HD signal.
Not long after the HD audio was lost the receptionist started getting calls from people saying they could only hear the station for a few seconds. If memory serves she received over 20 calls in one hour!
If you have a HD receiver you know you must tune to the frequency and receive analog audio for a few seconds until the receiver captures and buffers the HD signal. So people with HD receivers didn't know they had HD receivers! Seems to be a common problem - people have these HD radios in their cars but have no idea they have one or how to use it.