You don't want time for any non-mechanical verification because stopping a train needs to begin immediately if there are serious problems Poland is apparently

You don't want time for any non-mechanical verification because stopping a train needs to begin immediately if there are serious problems Poland is apparently in the process of purchasing and installing GSM-R, which is basically like old mobile phone (cellular radio) technology but specifically for Railways. Although GSM's security is hardly state of the art it would definitely be reasonable to call that "verification" if they had it. The "easy" way for lay people to send such a message under GSM-R would be to obtain a real transmitter, maybe steal one. Presumably since they're buying GSM-R they currently have either an ad hoc secure system or they don't have a secure system at all and so in the latter case yes there would be no verification.