Not to sure how i feel about this, would central banks just run full nodes themselves and if they did how could we trust the money supply. there are i'm sure plenty of questions here, but it is interesting to see their interest is there.
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the keyword you have to pay attention to here is "blockchain" and blockchain is not bitcoin it is the technology that bitcoin and a couple of thousands of altcoins are using. when a bank starts integrating its system with blockchain, we will end up having bitcoin and a couple of thousands and "one" altcoins!
and they are interested only because the blockchain technology is interesting and also beneficial in many aspects for them to use.