True, the Germans did have what we today would call GCI but as I recall it, there were some pretty funny episodes connected to this since Allied Intelligence soon began to try to take over and direct the intercepting German flights in the wrong directions, with verbal battles going on on the German frequencies with both real and fake German GCI officers saying things like: " No! Listen to me! I'm the REAL controller!" The other one is a British imposter! LISTEN TO ME!" and vice versa. IIRC then the Germans tried to counter this by using female controllers, to which the Allies of course responded by using their own female German speakers to impersonate them! ECM, ECCM and ECCCM in its infancy!
Yes, I think this is recorded by R.V. Jones in his book "Most Secret War", for British Night Bombing. Night bombing had particular requirements for GCI, in order to help the fighters find the bomber stream. In daytime, the fighters would hope to use visual engagement tactics but, the early warning leading to optimised launch times and guidance for routing to intercept the raid and escorts was more like the use of CH Radar in the BoB during daytime raids. Here, in 1944, I am unaware if real-time listening provided Bogey-Dope to the Escort fighters?
Eng