Last I knew Metro Taxi was still operating under the taxi frequencies in the VHF-High band. Now remember they are not only in service in New Haven, but also operate in Bridgeport, Hartford and I believe in Waterbury. So check for the licenses in those cities too or just do a search through CT instead of a specific town / city.
Also, taxi companies don't operate with repeaters or simplex. To listen to them you need to have the dispatch and the taxi transmit channels. The drivers cannot hear each other, just the dispatcher for the purpose of "not stealing a fare". Just wanted to pass that on to you.
Also those licensees are not for trucked use, they are conventional frequencies.
UPDATE: - The only frequency I am getting data on is on 152.27 & 159.495. This could be a MDT transmission for them, unsure though if they do that.
Here's the frequencies I found and are they the same that you have?
WNUV448 - 152.315, 157.575
WNJS878 - 152.2625, 152.27 (data), 152.2775, 157.5225, 15753, 157.5375, 159.4950 (data)
Also under another license: 152.42, 152.45, 157.68, 152.71.