I had a chief dispatcher once tell me that a police blockade is just like having a derailment (without the damage) If the crews (both freight and passengers) wern't getting paid while they sat they would have tried to get the laws changed forcing law enforcement to hurry up!
I believe in Mexico the crews or first arriving law enforcement can take a quick report and drag the trespasser out of the way so the train can continue on, unless the crew cannot go on.