I work in automotive for a major car maker. Going the environmental route will not work!
I actually would play on the environmental thing...from a PR angle, at least. Given the grumbling about the tougher emissions standards being handed down, they could very well see the logic behind spending a little money on providing lockers for bike commuting and creating the appearance that they care. Huge companies love good PR, especially when they're being looked at in a negative way already. A friend of mine working at an automotive plant in Canada was able to obtain more recycling bins around the facilities using this same angle. It might be worth a try.

Good luck!