was told that hydrants prevented the usage of CSVs in my water treatment room, although I dont see why.
When the water consumption flow rate is less than the flow rate the pump is capable of delivering, the CSV device will reduce the flow from the pump to match the consumption rate after the CSV. When flow from the pump is reduced, the pressure will increase so with yard hydrants located before the CSV, the hydrants will experience excessive water pressure which maybe 150 psi when only a small quantity of water is being consumed after the CSV.
For the pressure to the yard hydrants to be identical to the pressure delivered to the home fixtures, the hydrants will need to be plumbed after the CSV. Depending on the diameter and configuration of your well casing and supply piping, it is sometimes possible to install a CSV within the well casing or nearby to the well so every fixture after the CSV including the yard hydrants, will be supplied with constant pressure as controlled by the CSV.
I assumed the same for the Cycle Sensors as well.
A Cycle Sensor monitors the electrical power consumed by the pump. When the pump is moving the maximum amount of water possible, power consumption will be highest and will reduce as the flow rate is reduced or the height of the water within the well rises. If there is insufficient water remaining in the well to cause the pump to draw air, the amps will drop too low which will cause the Cycle Sensor to shut off the pump. Since a Cycle Sensor only monitors power consumption, the location of the yard hydrants will have no bearing on Cycle Sensor operation.