The (flawed) theory of government stimulus plans is that in certain economic under-capacity situations, government spending can have a multiplier effect.
The Anti-planner shows that, as far as government spending on mass-transit is concerned, $9,150 of taxpayer subsides per rider generate about $6,100 in average savings per rider. Every dollar of public transit spending destroys about 30 cents of value, which I guess makes it the anti-stimulus.
Update: Yeah, I know, transit supposedly eliminates all those externalities. But most rail transit plans typically reduce congestion by fractions of a percent, even by their builder's estimates, while energy savings is wildly over-estimated.