You would think, but it doesn’t work that way. It’s not just the label, but the signal that’s sent to the computer when you press the button.
If you plug a windows keyboard into a mac, it acts like there’s no option or command. You can manually edit the character map so that Windows acts like Option and Alt like Command, but this only takes effect once OS X has loaded so you can’t use bootup selections like Command+V for logging mode or Command+S for terminal mode.
I don’t know if windows has a similar function to remap a mac keyboard. It’s basically a huge pain in the ass. If you’ve got a mac, get a mac keyboard, if you’ve got a PC, get a PC keyboard.
(Also, come to think of it, a mac keyboard has the CD eject key, but if you plug in a keyboard without one, OS X provides an eject menu in the title bar.)