Are these batteries compatible with one another?

My digital rebel (300D) takes a BP-511 battery (of which I have 2) ... the 40D only lists the BP-511A (the 30D says it'll take BP-511/BP-511A/BP-514/BP-512). I know that the 40D isn't out yet (actually, it supposedly is, since the release date was changed to today, but not sure if anyone stateside has gotten theirs yet), but does anyone have an educated guesses as to whether the BP-511 from my 300D would work in a 40D?

I can't really find any good info on what the difference is between the BP-511 and the BP-511A ...

I'm guessing it will be compatible, the only one that I know doesn't work and uses a different battery is the Rebel XTi

which is a NB-2LH for reference.