It would require however that there are other couriers that fulfill their safety requirements with the logistic infrastructure to deliver to the entire country. That's not likely. But entirely within the realm of possibility that someone with deep pockets could start one.
However it would not make any difference for Tesla, as that courier would also be unionized. Few other companies would do business with them otherwise, as Tesla is about to find out.
You can’t have a “should not respect strikes” clause in your tender, especially not as a government agency