Thats such a cool design I wish my PowerBook 1400 had that. I believe I read in another thread that somebody tried it out and they were interchangeable.
Or even more likely, it will simply not charge the battery while the machine is running, and charge it very slowly when its not. This is how the old PowerBook 1400/Duo/3400c/G3/iBook adapters worked. If you connected a low power Duo power supply to an iBook or PowerBook G3, it would simply maintain the same battery level while running - no charging.
I believe this was even documented in a TIL article at Apple's web site.