Seriously? I find it very unlikely this is the work of a "lone wolf developer". Newag management and executives knew about this. Some of these trains were configured (poorly) to "break" at a scheduled date that just so happen to line up with when those trains were scheduled to go get serviced[0]. Lone wolf developers usually don't have the ability to make builds/configurations for a particular deployment of the software...
[0]: https://badcyber.com/dieselgate-but-for-trains-some-heavywei... - Section "Checking the date is hard"