No, they wouldn't do that. If they were going to replace the matte painting in post, they wouldn't use a matte painting. They would use a blue screen or a green screen background. The matte painting is too complicated, which would make it too costly and time-consuming to replace.How do we know that an acurate matte image placed in the Tardis in thos pics? I'm guessing they put a generic matte image in the Tardis for principle shots, then replace it with a CGI live action element in editing.
Thats true, for further away shots i'm sure the matte is good enough but for more close up shots though the door the matte is probably replaced with a greenscreen back drop.