Cops control, beat, and arrest people.
First, I apologize for my links...the one from FT seems unavailable now and the other is in german. So your misconceptions are excused too.
When you look at a map you will see that Brandenburg shares a long border with Poland. A border which has been for years quite easily to overcome for criminals from both sides. So for years german and polish cops and investigators worked together already....that is nothing new here.
The other reason for that that was stated explicitely was the rising numbers of refugees and immigrants since 2015. Even as the overall crime decreased in Brandenburg the people got more nervous and demanded a stronger police presence. But Brandenburg, like many other Länder, hasn't has the people available to increase the numbers of cops at will and so suddenly.
Asking the same structures which whom they have worked closely together for years seems a logical step.
NOTHING but really NOTHING points to a situation where future german cops will control, beat and arrest Poles in Warsaw!!!
It might be much more possible to see future polish cops control, beat and arrest unruly foreigner in Brandenburg...now wouldn't that be cool...
That is Brandenburg:
I found another link in English: polandinenglish.info/39409600/german-police-recruits-from-poland