They were using the Western States Contracting Alliance (WSCA) $37.99 unlimited plan for data devices, its a perfectly normal plan. Here in Seattle we use it for our busses WiFi Hotspots, on AT&T it is truly unlimited.
WSCA allows throttling if you’re a top 5% user locally. Not a problem in the middle of Seattle, but definitely something to plan for a command vehicle responding to wildfires and you have a high density of responders... particularly since the problem is so cheap to fix.
Also, another jurisdiction like police, state emergency management, Feds, etc may have a plan that allows them to deprioritize you at any time. If they were in FirstNet, a machine to machine plan, or a Verizon public safety plan, there would be no issue.
