As you say, there are dozens of examples where Batman loves. He isn't a machine. But his love tends to be obsessive with a fear of loss as its basis. So essentially what is being asked of Batman most of the time is to overcome his fear of loss and to stop trying to control everyone around him so he can be with the person that he loves. He went through this most recently, arguably, with Damien. Morrison had Bruce turn and focus that fatherly love into Batman Inc., and he ended up ultimately losing Damien (exactly what he feared). I do think it was shown that Damien found Bruce's love to be enough, but at the same time he saw it as self-destructive.
Selena has brought out a different kind of love from what we have seen most of the time with Bruce - playful love. He gets so infatuated with her and her shenanigans that he'll drop his vow and ignore her crimes just to be with her. Joker might not have been that far off with his assessment. He should know, because he's one of the few who can also bring out Batman's playful side (granted in a "dark mirror" kind of sense).
So while I do think the overall topic of how Batman deals with love is trodden ground, this story may deal with new aspects we have not seen before