I think it's fairly certain that we can quell the "rumours" of Assad and the ISIS rebels being allies, since this incident confirms that Syria is indeed fighting the rebels. If Assad and the rebels are indeed allies like several people claimed, then there wouldn't be conflicts between Syrian soldiers and the rebels. It's also interesting to note that despite American air strikes and "American air superiority", the rebels can still maneuvere quite well in Syria and Iraq, and that they're still capable of fighting the elite Iraqi Army and the battle hardened FSA organisation and the Syrian Army.
It's going to take a lot more than American air superiority to defeat the rebels.