Fwiw, Songza is actually in Google Music. Google bought Songza a while back, and a couple/few months later Songza playlists were available in Google Music.
It was nice because i could then cache my favorite Songza playlists and cache them on my Google Music App. Handy
For sure, that's part of why I love Google Music. They included Songza's "mood and activity" playlist picker, which is great.
My biggest issue with Songza was the lack of selection. They have some great playlists, but after listening all day they get pretty repetitive. Google Play seemed to have the benefits of Songza with way more selection.
It was nice because i could then cache my favorite Songza playlists and cache them on my Google Music App. Handy