There never were close to 16,000 workers there were about 800 construction workers few of which were working at the time because the pipeline was not actively being built.. When it was complete there would have been under 50 workers, both Canadian and American who would have jobs.

The pipeline was never for providing anything to the US it was to get access to a shipping point to send tar sands to China to build roads and tar sands oil to China to use in the manufacturing of plastics and other oil manufacturing process.

Most got other jobs in pipeline construction. There are other pipelines being built.

Why coding? What a weird thing to see as the only other option. In an economy with a 3.5% unemployment rate they will have no problem finding other jobs. If they are union or not depends on what jobs they choose to take.