Measuring sensor with two PLCs
a voltage signal can be shared between PLCs if they both share the same ground voltage.

that said the sensor needs a 24V supply that supply should be provided in such a way that with one of the PLCs turned off there will be no malfunction. 
this may mean  carefully chosing which PLC is responsible for powering it, or powering it from both using a pair of diodes to prevent back-feeding power.

current signals  (eg 4-20mA loop) cannot be shared as easily.