Very good question and I'm afraid I don't know -- but I suspect that they aren't. I've not disassembled the CO Sonic but have seen it done in threads in the past where people have chopped them up to use the sound modules for their fan-made replicas.
I haven't taken my RT Sonic apart except for briefly when I first received it. There was an issue with the battery compartment, taken from the CO Sonic but modified into a single removable unit, not holding the batteries in place. I folded up a small piece of paper and placed it against the batteries so that they wouldn't pop out. Here's a youtube video (not mine) that shows how it comes apart starting at 5:50