They're reasoning so far for why silicon and carbon can or can't be fused together is that I'd be very unlikely. That's like saying nobody would ever win the lottery because the odds are so low but every now and then we hear on the news that someone has indeed won it, so therefore no matter how unlikely if it has a small chance it is indeed possible.
Yes, it is possible that carbon and silicone-based life forms can be fused together, because this is already being done with modern medicine. Prosthetic limbs for amputees, as well as artificial hearts, already combine the human body with the things that technology can do. As science progresses, eventually there will be complete fusion between these two things.
It is not possible with our knowledge now that Carbon and Silicon based life forms could be fused together. Silicon does not have the ability to connect with other diverse atoms for chemical versatility required in metabolism like Carbon does. Silicon also has difficulty forming dual bonds. It is very unlikely based on our knowledge of biochemistry that these life forms could be fused together.