That system is track circuitry that uses relays to detect rolling stock when they short the two rails via their wheels. That exists widely, and it identifies that rolling stock is present in a track section. That same relay also locally (as in, on the ground at that location) triggers any signals to switch to red.

Controllers can’t then give authorisation to another train to enter that section, nor can they override any red signal. In cases where it applies, they also can’t remotely control track switches to enter this occupied section. However there’s nothing with that system that then controls the rolling stock itself, so a driver can still SPAD if they don’t see or ignore the red, and the remote network controller absolutely cannot stop a train that is hurtling towards an occupied section. That’s all on the driver in the cab.

Fun fact: track clips are used by track gangs to short these sections in lieu of a big axle sitting on it, which is one of the methods of providing site control to the gangs so trains don’t enter their worksite. It’s certainly not the only one, though.