Uber ad on a taxi?

While in Berlin, I saw a taxi cab with an Uber ad on the side of the car. Yep, you read that correctly. An Uber ad on the side of a taxi car. 

After I got home, I tried to dig up some dirt on how this could possibly be allowed. I didn't find much, but I did learn more about Uber's rocky relationship with Germany. 

In early 2015, Germany banned Uber because it was "unlicensed taxis operating as a business". I don't fully understand all the issues pertaining to Uber vs taxis but I know that many cities and taxi drivers have not been happy with the ride-sharing company. 

UberX is now allowed in Germany and drivers are required to have special permits for commercial transportation of passengers. 

I still haven't found anything conclusive about Uber and Taxi companies partnering or Uber being allowed to or even wanting to place ads on a taxi cab.

I don't know what to make of this strange ad placement, what's your take on an Uber ad on a taxi?