Well, it seems that Black Museum proves fan theories that the whole show exists in the same universe true.
From the interview with Charlie Brooker with Digital Spy,
In our exclusive interview, Brooker reveals the surprising reason why the Easter eggs started, and how upcoming episode 'Black Museum' connects Black Mirror's disparate strands.
"It does actually now seem to imply that it is all a shared universe," he reveals.
Above article contains a video of full interview.
From Heavy article,
Brooker said: “It used to be that we would refer to other things partly because it was convenient… As time goes on we’ve put more and more of these nods to other stories in, and certainly this season for the first time … the first very explicitly, one of our episodes, Black Museum, has got very specific references to previous stories we’ve done, and it is sort of filling in a bit of backstory there. You don’t need to have seen those to watch the show… But it does actually sort of now seem to imply that is actually all a shared universe, which was the opposite of the answer I used to give to this question.”
