Syracuse city fire uses Digital Vehicular Repeater Systems (DVRS). I believe they are in the chiefs vehicles.
Tac 2 on the digital network is linked with Tac 12, which is off-network and being used as a DVRS. When car 2 is dispatch, units will use Tac 2 & 12.
Tac 3 & 13 for car 3, and tac 4 & 14 for car 4.
So far, I have confirmed (and added to the DB):
453.1125 (156.7 PL) Tac 13 (DVRS to Tac 3)
453.9125 (156.7 PL) Tac 14 (DVRS to Tac 4)
Usually installed in the trunk, the DVRS extends ASTRO 25 comms when the firefighters are outside of the truck, like when inside a building or in an area without the best of coverage. Keep in mind when they use tac 12, 13, and 14... you will only hear the offnetwork channels when they are close by becuase the power is low. But if you listen to tac 2, 3 & 4 for City fire, you will hear the entire converstation on the digital network.
Tac 12 is somewhere under the WQKP307 license. Plug em in, log what you hear.