Why passenger fleets are held to a higher standard
AIS-140 was introduced after a series of passenger safety incidents, and the emergency button requirement follows directly from that.
For a taxi fleet the practical consequence is that the device is tied to the permit. A vehicle whose device has stopped transmitting is not merely untracked, it is at risk at the next permit or fitness renewal.
The failure is usually silent: a lapsed data plan or a device never registered on the state backend. Both keep the unit powering on while the state record goes quiet. See the VLTD backend.