I'm interested in this as I've been trying to get the same answer for a few months.
I have an endless style game in C2 which is pretty much ready to publish if I can add google play high score / services.
I've seen we've all been posting for this over the last 6 months.
Please hit me up on discord or skype as I managed to get a couple of ways working.
I've managed to get it logged in and leader boards / achievements showing.
I am using C2 and building with Cordova CLI
(I am on discord as Mayfly and skype as mayfly118)