The closet thing I know of is this: https://krmax44.de/playify/
A chrome extension that allows you to open Spotify links and playlists in Google Play Music. Check it out and let me know how it goes.
Yay there's 2 of us! Those are all stations from GPM, not playlists I made, but I do think you can listen without being a subscriber too, since they were part of songza? I've been able to share personal playlists with friends who don't subscribe too, they just play ads occasionally and don't include music I uploaded and isn't in GPM's streaming catalog (but I think that would be the case even if subscribers listened in). /r/allaccessplaylists exists too, just fair warning if you share a personal playlist, it does show your name, photo, and links to your google+, which is sketch when sharing with complete strangers, unfortunately.
Also there's a chrome extension that turns spotify links (playlists and song links) to GPM links, it even opens them in the desktop player if you have it installed, so that's cool!