You're right, I don't have any personal insight in this chip, I just say what a little bird told me- however...

Most "manufacturers" outsource the actual manufacturing process to other companies, so yes IBM still builds the chip under the Microsoft brand :)
But it doesn't mean Microsoft are forced to use IBM as the builder, if they find another plant they could move the construction there.

And yes IBM still owns the underlying PowerPC core, nothing stops them from reusing solutions used on this chip. They just can't offer this product to other parties as it is.

Just curious but what enchanted floating point capabilities? the only difference except for multiplecores are the extended vector instructionset (VMX-128) afaik.