I had always suspected his car had been used but since CJ was absolutely baffled concerning his arrest and is suing the police, I'm not so sure.
I wonder if a more likely scenario is that VT took the car without CJ's knowledge? As I recall, all the residents had access to the main hallway from where they'd collect their post. If CJ had, perhaps absent-mindedly, left a car key there VT might have "borrowed" it during the night when CJ was tucked-up in bed.
As CJ lived alone, he would probably have had no alibi, had his car been seen on CCTV, hence his arrest on suspicion of murder. The police may have released him when they were sure he was not the driver, but kept him on bail until they had enough evidence to indicate that he was not an accomplice by knowingly lending the key.
Quite a few "ifs" there, but it does seem to me to be a possible scenario.