Your argument is based on an incorrect understanding of liability, and is also nullified by the fact that these measures, allegedly justified on safety grounds,

Your argument is based on an incorrect understanding of liability, and is also nullified by the fact that these measures, allegedly justified on safety grounds, were not just undocumented (see other sources) but clearly deliberately hidden, to the point where the manufacturer pretended not to know why the trains would not start. Update: here's a quote from the Ars Tech. article itself, showing a) no tampering with the trains' software or hardware was necessary to get them running, and b) there's no even slightly plausible case for believing the manufacturer was unaware of this. Furthermore, if it really was somehow unaware of what was going on, then these 'features' cannot be justified as a safety measure. Dragon Sector got the trains running after discovering "an undocumented ‘unlock code’ which you could enter from the train driver’s panel which magically fixed the issue." Update 2: It is barely plausible that the ability to track the trains' presence in other maintenance shops was initially added to gather evidence for liability and warranty purposes, and then someone had the dumb idea of using this to covertly disable trains when this happened. Note that the use of a third-party maintenance operation was not a secret: the train operator solicited bids for the work, and the manufacturer tendered one. Clearly, third-party maintenance was not in violation of any contract (and if somehow it was, the manufacturer did not need to gather any covertly-acquired evidence for a breach-of-contract suit.)