The majority of taxi companies no longer use radios and just communicate via cell phone if needed. However, there still are a few taxi companies that use radios. Is there a specific taxi company's frequency you are looking for?
From my base in NY i can pick up some freqs from Jersey and i have received a few NJ taxi freqs
One being 452.050 DPL 315 which is called "Supercab"
The other 2 may be part of a LTR trunk system 471.4375 and 471.9375
I have got LTR LCN 16 for 471.9375 but havent yet got any LCN for the other one
Not sure if these are in the immediate area your looking for
Also try some freqs like 152.300 152.330 152.405 152.450 those have been known as "Taxi band" in the past many taxis have used those freqs some still do
some other common taxi freqs are 152.390 152.420 152.435
note that when taxis use the 152mhz freqs in many cases they will use it half duplex as the base channel
with the mobile channel being somewhere around 157mhz
some 157mhz freqs are actually boat channels as well