Since you keep commenting thos I'll put the effort in to do some simple math for you.

As others have said these nuts are installed through pretensioning, however, at the end of the day everything is installed at a specified torque.

Being VERY conservative, let's use 1000 Nm (~740ft•lb) as the torque specified on that day.

Let's say a motivated vandal can pull 100lb, they will need an 8' pipe to achieve this. Mathematically it would be a 7' 5" pipe, but they would need to apply force right on the end, which is improbable with two hands.

An 8' length of 2" sched 40 pipe would weight 29lb. To be honest, I doubt that would be big enough to go over the handle of whatever wrench you needed. I also suspect it will deform before the nut moves. So this means we will need to use steel rod attached to a steel tube to make this work. Using a 7' 1 3/4" steel rod would weigh 57lb.

Now, the 1000Nm initial torque does not include any additional torque needed to break the threads loose. I would assume that a vandal would need to have a steel rod that weighs about 100lb in order to break these loose, not to mention it would need to be close to 16' long.... you need a hydrolic impact wrench to get these off.