They couldn't. However, it looks like a remote rural road, not frequently utilized. Assuming the roadblock vehicle was waiting on the dirt path, a simple text message, like "almost there" would give more than adequate time to set up.
The fire was called in god knows how long after the fire started, and IIRC the response time was listed in MSM as 6 minutes. Judging by the condition of the vehicle, I'd speculate it burned between 15-20 minutes before the report was made.
I live in a similar area, we have rural roads where you could go an hour or more before you saw another car.
The reason those gates are there are to prevent people from doing shenanigans on those private properties, because they're remote, and not monitored frequently or easily.
Thank you for asking.
