In the past I have heard TX Army National Guard helicopters on 46.800, 139.100, 242.600.
According to the VFR Supplement few years ago they switched to 36.900, 134.100, 247.400.
I have heard them in the past couple years on 247.400 and 242.900 but haven't hear any activity on the others.
The helicopters that are used for firefighting and law enforcement have high band FM radios (probably multiband Wulfsbergs or something similar).
Last year when we had all the wildfires in my area I only heard NG helicopters on the statewide interop frequencies and Texas Forest Service frequencies but didn't hear a peep on any of the NG frequencies.
When they had the flood in Wichita Falls in 1982 the TX National Guard ground units used 41.000. I have seen that freq listed before so it is probably still good.