Would anyone know when this conversion took place? I understand City Island today is a popular mini resort town of restaurants. It is a little island off the Bronx and is somewhat out of the way, so it misses some of the craziness of NYC.
Anyway, as part of the ANC conversion, the Bell System experimented in New York State with intentionally non-pronouncable exchange codes, such as TT. Others were used as well in NYS. This was an effort to get more exchanges out of a district using codes that otherwise wouldn't be named.
I forgot to mention one of the reasons for a uniform name list was local pronounciations that might be different if spoken remotely to a long distance operator. Philadelphia had one exchange, BAring 2 (in West Phila), but it was pronounced bear (as in teddy), not "bar" (as in drink).
In 1975 I knew a politician who had a phone in his car. To reach him was by a regular 7 digit conventional phone number (LOcust downtown), so a casual caller wouldn't know they were reaching a car. I think when he dialed out he merely dialed the number.