The accuracy of current GPS for this application, when "reality" testing it against other embedded (route/track profiles/speeds)and acquired data (signal indications, location, and track/train speed) in a fully integrated PTC system is not really a problem that can't be easily overcome. The cost and design redundancy for integration of GPS seems to be more of the sticking point and/or proprietary turf fight on this issue?

GPS accuracy is not a real problem for this application. We do this level of tracking with GPS for trucks to within 3 feet or less for security tracking every day. And, I've tracked transit buses to within less than 1 meter of the on-board GPS unit, with good conventional civilian GPS reception and coverage. Linking the reported location to compare it to the embedded data, with rapid update, and "dead reckoning" from last reported location, also eliminates most of the "dead spot" issues in "canyons" and "tunnels".

Isn't the rule change more of an indication that the railroads are being effective in lobbying to consolidate significant volumes of hazmat routing on already PTC mandated shared "passenger" mainlines, and to "exempt" from PTC, as many "non PTC" miles of secondary hazmat feeder routes?

Well, I'm absolutely shocked to learn that!