Actually, I'm pretty sure those are Hubbell MOV style arrestors. The "600v" wiring on the line side is factory provided. The fact that it is 600v wiring is of no consequence. Keeping your distance phase to phase and phase to ground is.
That being said, installing arrestors in a padmount is a horrible design. When the arrestors blow, it is almost always violent. And they can take out the other phases in the process.
