Is it legal to use cell phone while driving a semi? Stopped at RR crossing.

Truck is at dead stop. Brakes set. Train ahead, cars behind. I am not moving until train is clear. I am in control. But only thing of interest is how long train is going to be?
Stopped at stop sign, even traffic light I understand. But parked similar to if traffic accident. I do not know if I will be parked for a minute, 15, a hour.
I was in POV few year back in MN winter. Accident with fatalities ahead. My +45 minute grace period before Dr. visit. I had intended to eat at hospital cafeteria as HCMC has dang good meals, at reasonable costs. I called Dr. they had heard about it. Well over a hour late I finally go there. 2 hours on interstate with car off as long as I tolerated temps. It was above freezing so hat, gloves in car was not bad. You bet I ran my phone battery down.

 

Traffic lights are seconds. Trains backing up, switching tracks to add, subtract train cars we are talking parts of a hour. Often in 10 minute area. We are not talking a train going +30 mph under 100 cars going over a crossing. In car/pickup I turn around, go about 2 miles over. To a bridge over RR tracks. Then backtrack. But semi/trailer a bit harder to turn around, side streets I might not be legal…