Not if they chose one of them as base and incrementally improve it with code taken from the other. Easier to test and stable at every point.
If there is insanely great stuff in the intersection you mention, it probably constitutes a research project, which it would make sense to undertake in the background (if at all). For Oracle, the only "insanely great" that counts is that which yields benefits that customers will pay for now/soon - not what's technically impressive. They're a sort of microsoft-research anti-particle. disclaimer I actually have no idea.