A CEO has the responsibility to look after shareholders, but as a citizen, I want my government spending my money only on the proper functions of government. Picking winners and losers is not a proper function of government, and neither is building this tunnel that Musk wants to play with. To the extent that Musk pushes government outside its proper role, he is harming the country that most of his shareholders live in.
As far as I can tell he’s using his own money for the tunnel. His goal is to reduce costs by at least a factor of ten.
There’s a biography of Musk that I suggest everybody read, so their blood pressure doesn’t go up due to misconceptions about him.