Via The Early Days of a Better Nation, a pointer to this wonderful party political broadcast by the Scottish Socialist Party.
As Ken MacLeod points out, this video is so cute that “You can disagree completely with the policy and still find yourself smiling.”
I'd add that although I can't speak to the cost estimates (or the relative value of the things to which the cost is compared) the basic economics underlying the proposal are straight out of what I recall from my college public welfare economics course: mass transit is a public good because every user of the bus or train reduces the number of cars on the road, thus increasing the value of the (less clogged) roads for everyone else. Thus, the socially optimum price of mass transit is actually less than the profit-maximizing price (because the price fails to give credit for the positive externalities), and likely to be a price that runs the system at a loss. In a world free of transactions costs, pricing mass transit at zero is probably below the socially optimum price, but there comes a point at which collecting the money costs more than it is worth, so free transit may be economically rational. Politically, of course, it is also a visible symbol of what your tax monies are buying.