I'm not sure where you read that, but the exact opposite was true. NYC was and still is very heavily invested in T-Band for public safety, and fought tooth and nail for years against the T-Band giveback legislation of 2012 (which was eventually repealed in late 2020). Even while the giveback was still going forward, the NYPD was already planning the migration from analog to P25 on their T-Band frequencies. The FDNY went forward with having VHF take a back seat to T-Band for their primary dispatch channels (even taking them off the air completely for a number of years), and invested heavily in T-Band capable APX mobiles for all apparatus. DoITT (now OTI) also upgraded their old T-Band SmartZone system to ASTRO 25 on the same T-Band frequencies. They briefly flirted with a 700 MHz cell for the ASTRO 25 system, but instead upgraded the 800 MHz SmartZone cell to ASTRO 25, operating on the same core as the two T-Band cells.From what I had read at the time the T-Band was selected for takeaway thanks to NYC. They had plans to move from there and were looking for a way to finance it. The story (true or not) was that the frequencies and the dates coincided with their plans, any other users of T-Band around the country be damned.
Bottom line is that there would've never been enough spectrum on 700 or 800 for NYC to abandon T-Band, and so any alleged "plan" for the city to do so with the FCC footing the bill would've been completely impractical.