The app previously acted as client for songs stored in your Google Music library, but with an update to version 6.0 today the All Access subscription service is now officially available to iOS users. The changelog on iTunes also lists the ability to “Create/play Radio Stations” and “Search, listen, and add music to your library from inside the app.”
As for why Google didn’t make it’s own All Access app for iOS, we’ve heard from sources close to the situation that Google wants to submit an app but is currently in a holding pattern with Apple regarding what they will accept.
gMusic: Google Music Player is available on the App Store now for $1.99. The updated app will require users to have a Google Play All Access subscription to access the new features.