I was just having this conversation with some folks on the MSN CB450 site (which, by the way, is an excellent gathering place of old 450 buffs). Here's what I've got for you:
It didn't work on my CB450 despite the fact that, technically, it ought to. Here's the theory: if it has fixed magnets, it'll work. If the magnets are electromagnets (coils spinning within coils), it won't. Basically, a battery eliminator is a capacitor that acts as a very short-term battery.
In practice, my 450 just wouldn't start with a battery eliminator - just couldn't get enough charge from the kick to make it happen.
However, here's a funny tale. I've wired out the key switch on my bike... I've got a nicely hidden SPDT switch that takes the battery out of the loop, making it just about impossible to start my bike without the key. Don't ask me why I thought this was a good idea. I'm pretty sure alcohol was involved. Point is, one day I kick it on and go riding. The thing runs like shit, but it runs. I got several miles down the road before I realized my battery was still switched off - so the bike had actually been running with no battery at all. Now, why it would do that but wouldn't run with a battery eliminator inline is a mystery to me... one of these days I'll bond with my voltmeter and figure that one out.