They would lose so much face. And they would have to pay Tesla, which they dont want to do. Even assuming that Tesla would do a deal with them, which they may not.
Tesla have stated that they are open to other manufacturers using the Superchargers, so I think they'd at least entertain it. Who knows what the price negotiations would be like, though.
Musk doesn't seem like the type to shy away from the unknown, so commence the price negotiations!