The navigation is not 'outsourced', Waze provides that.
The POI lookup uses the external providers on the search result screen per their logo. Bing, Google, Yelp, and FourSquare.
Street address lookup is done by Bing in the USA but the results show on the Waze results screen.
The result for both are GPS coordinates that Waze uses for routing.
If the external providers don't have the correct GPS coordinates for a POI or street address Waze will take you to the incorrect location. This can also be an issue if the location is in a mall or shopping center since Waze will route you to the nearest mapped road to the GPS coordinates. This can lead the being routed to the road behind the shopping center, a freeway ramp closer to the GPS coordinates, etc.
The tough thing is that each of the external providers may give different GPS coordinates for the same POI. It's difficult to make the Waze map fit every possible result. Sometimes choosing POI results from another provider gives a better result in Waze.
Wazer in San Diego, California USA and Tijuana, Mexico
iPhone 6 Plus, iOS 8.1.3, Waze 3.9