"meaning information shared between RBS employees is only accessible to other colleagues within the bank"
And Facebook itself. And by extension any law enforcement in the US.
I know that Safe Harbour (and its failure) only affects transfer of individuals' data, but it clearly emphasizes that American companies cannot be trusted at the moment. (Not necessarily because of their wrongdoing, but because they cannot guarantee that Uncle Sam isn't going to demand a copy of the data. This may very well include FB-for-Biz conversations between RBS employees and whatever else the platform has to offer)
Bottom line is: It is possibly the worst point in time to make such a bold* decision, while the effects of Safe Harbour's fall are not entirely clear. Common sense would dictate to hold off on such a deal for a bit.
*the article called it bold; I'd call it ignorant and stupid
Edit: I'm wondering if RBS are doing this right now, because FB paid them to get a foot into the door of serious business?