Talkgroup 7446 on Layer 2 is "TCFA Fire 1". It's been submitted to the database, but not added yet. From my very limited monitoring lately, I believe they're using this new channel as a multi-agency structure fire response channel, instead of Fire IO 8 like they had been doing in recent months. However, I've still heard activity on Fire IO 8 for recent fires. I believe there's a lot of changes taking place, and it's all likely to continue to evolve.
There are also
TCFA Fire 2 7448
TCFA Fire 3 7450
TCFA Fire 4 7452
TCFA Fire 5 7454
TCFA Fire 6 7456
Also of note, a Fort Worth City Council Agenda item indicates that Lake Worth and Saginaw may be dispatched by Fort Worth.
https://fortworthgov.legistar.com/View.ashx?M=F&ID=8277604&GUID=2B679BEA-EEA5-4579-AA07-DF4365A20266
You may have also noticed that Lake Worth and Saginaw units are now referred to as 110 and 114, 214, etc. I imagine the extra leading "1" is to help distinguish Lake Worth Station 10 and Saginaw Station 14, units from Fort Worth's own Station 10 and 14 units.
Ben