I guess it depends in part on how many cars have been fitted with DAB radios. I suspect most vehicles still have FM/AM radios, so wouldn't notice if DAB was replaced by DAB+.
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DAB+ as a mandated format is over ten years old now. Some other countries embraced it earlier, and to a greater extent than we have. I've not (yet) come accrss a factory fitted DAB car radio that can't receive DAB+, not too surprising considering that ten years ago very few car makers were fitting them, and only in top of the range vehicles (if at all) . I would expect the current receiver base of vanilla DAB only receivers to be non-car radio models and 'aftermarket' car radios.
I'm surprised the Beeb haven't yet dipped their toe in the + pool. It works very well, and (everything else being equal) gives equivalent subjective quality at less than half the bit rate of vanilla DAB. The DAB+ stations
on the SDL national mux are more robust in weak reception than the DAB stations on that mux. That didn't make sense to me, as they are all wrapped up in the same transport stream, but an expert from BBC R&D I got chatting to recently assured me that's the case in theory too.
