The problem is that PTC, depending on where you are in the world, is really a generic term and has different meanings. There are very specific implementations of different kinds of positive train control.
The Japanese bullet trains, shinkansen, have had complete automated train control in the cab, not dependent on signals beside the railway lines, since 1964, when those trains started running. As I mentioned, even American steam railways back in the 1920s, the Pennsylvania Railroad, for example, had mechanisms for positive train control, as did the Great Western Railway and other railways in the United Kingdom.
The technology has many forms and has evolved in many ways. You have situations like the one in Santiago de Compostela, Spain, where there was an older system interfacing to a more modern system, and the interface itself between the two systems was part of the cause of that accident.
The situation in Canada is that we only have the visual indications and the two engineers in the cab as the way of checking that. In the case of Burlington, that didn't work. There was a third qualified engineer in the cab. Although in training, he was a qualified and experienced engineer. That still did not prevent the misinterpretation of the signals there.
When I say positive train control, I mean a system that provides the second line of defence so that if there is a mistake made, or if a signal malfunctions, as it did at Saint-Charles-de-Bellechasse when the VIA Rail train derailed when the signal was partly obscured, there will be a second line of defence. That is the recommendation of the TSB.