Thought I would give this a test - registered my car SIM with Cubic and took a 30 day 2Gb data allowance to allow me to stream via the car SIM
Sorted out the wifi MMI connection and logged into my Amazon details via the MMI Connect app. Amazon Music then appears in the list of sources, so far so good
It lets me look at Amazon playlists but only to find that no music could stream
I think my issue is that whilst my wife has Amazon Prime membership which includes free membership to Amazon Music, she can't share that Prime benefit with my account (although I can receive some of her account benefits)
Amazon product
Kinda pointless me signing up for my own Amazon Prime membership - I'll stick to music on SD card or the radio!
*Edit* - found a workaround for the Prime account sharing issue - logged out of the Amazon account on both MMI connect and the Amazon app on my iPhone. Logged in to Amazon app under my wife's details, then logged back into the Amazon section of the MMI app - it now recognises my wife's details
(I then logged back off from her details on the Amazon app itself, so I can't see what she spending money on, lol )
I can now stream free Amazon Music using my iPhone - music comes through pretty quickly, but then I live in an area with reasonable 4G coverage
My next company car in a few weeks will be a BMW of some description - will be interesting to compare their streaming options with the somewhat convoluted method here.