Yeah, it is certainly possible, but I am not sure how the game teams handled this (I would have to ask them). It is certainly not something as easy as calling some method. Maybe you can specify what exactly you would need for your application and we can figure out an easy way to do it.

Currently native APIs like In-App-Purchases, Flurry, AdMob, etc. are all integrated into the BuildSystem and will add required classes automatically for you (because it was needed in multiple game projects), but generally adding something native is not always easy because of the underlying technology with Xamarin. However there are tons of tutorials and helpful libraries out there :)