I'm not sure this is news, But I see that
@Dan hasn't mentioned this in his post, and I've also seen him reply to a comment there that there is no way to transfer Spark Cash (from the Cash card) to miles.
I can confirm that I have been approved for both the Miles & Cash cards (using the 2bm) and was able to transfer cash rewards to Miles!, and it was quite straight forward. the option is there and the transfer is instant.
I think that makes this whole deal much more attractive.