Wow, this is an excellent list!
Apart from BBC Radio, I had no idea of the breadth of the revival in "radio" drama! It makes sense that an independent movement would flourish given today's ease of distribution. But I think the X-factor in radio drama's survival is just that it is such a fantastic medium for storytelling. The way the inner visual centers of the brain light up when you are fully immersed is certainly worthy of some kind of neurological fMRI analysis ;)