I just updated the google play services lib to ver 15 to find out that MapsInitializer.initialize method no longer throws GooglePlayServicesNotAvailableException.
In the description of this method it now says:
Initializes the Google Maps Android API so that its classes are ready for use. If you are using MapFragment or MapView and have already obtained a (non-null) GoogleMap by calling getMap() on either of these classes, then it is not necessary to call this.
So, I guess if you have already called getMap and you have gotten a map object back, there is no need to call this any more.