All businesses can benefit from bitcoin, not just for money saved through fees but by the free advertising they get by accepting bitcoin.
It's the novelty effect at play here. I would imagine they would actually be at a loss every time they accept bitcoin payment. The restaurant can save 3%-5% from card fees, but they could loose out on exchange rate and conversion fees. Bitcoin a great marketing tool. I would dine in one of these restaurants if I have a chance and have fun spending bitcoin.
I hope they accept zero confirmation payments? I do not want to wait around for confirmations. We all know there is no telling when the next block will be mined.

It's not really novelty as most bitcoiners want to spend their coins. And they wont lose money because they will almost certainly use a payment processor such as bitpay that gives them the dollar value at the time of transaction.