Yes traditionally and in the Arkham series Gordon or a GCPD higher up mans the signal not that it matters because signalling for Batman to come… means Batman comes and just kicks 47’s ass.
If 47 existed in the DC Comicsverse then it is over before it begins. Batman has a comprehensive of the world’s peak assassins and mercs from your Deathstrokes to your Lady Shiva’s he already knows the ins and outs of an assassin repertoire and he plans accordingly.
Also Batman is not stupid enough to not look for trackers or listening devices. He has been a vigilante for 75 plus years sure it happens sometimes in the comics but not a common occurance.