Much of the work for the light rail was done on Shabbos. If it took 3.5 years, then a half a year of it was done on shabbos. Is the light rail forbidden to use for a half year?
The rule of waiting “bkdei shyaasu” only applies to the work that a gentile does on shabbos, and according to many poskim even the work of a non religious Jew on shabbos. However regarding the light rail, although the work involved a tremendous chillul H-shem, it would not be forbidden. The reason is because there is plenty of time that elapses from the time the actual melacha was done until the light rail is actually used. For example the melacha that was done in laying the tracks, there can be a few years from then until the train actually starts to run, as time is given for the electric work to be done etc. Technically the tracks can be laid then also, therefore it would included in the time for bkdei sheyaso. Aside from this there is also a lot of time that elapses because of technical reasons that they don’t work, wich would als be included in the time of bkdei sheyasu.