Personally, I doubt it ...
A long time ago I was looking into writing an emulator and at that time the general consensus was that it took between 8 and 12 times the processing power to do proper emulation in software without doing instruction translation; and instruction translation is far buggier and has massive compatibility issues. Now, unlike the XBox (which had a hardware abstraction layer for the GPU), the PS2 hardware was quite regularly directly accessed from code which means that you need a high level of hardware compatibility for most programs to run well.
I suspect the Cell Processor is probably fast enough to emulate either the Emotion Engine or GPU from the PS2 without using SPEs but I suspect that it would require most/all of the SPEs to emulate both processors at the same time. In my opinion this would be a nightmare to develop because you're attempting to emulate a sequential system on a parallel system and you need nearly full processing power from the parallel system and a high level of compatibility in the final system to get most things to run well.
Is it possible? Probably, is it likely? not really ...
