.I think there's no hope for Safari on Mavericks to get restored push notifications ability and here's why:
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If the same notification system is in play site wide then Safari won't receive them which is a pity because only through Safari you can get notifications arriving right at your desktop without the browser being open while you have to keep Firefox or Chrome open to receive them which is highly inconvenient.
Meanwhile, I came across sites that do offer push notifications compatible with Safari 9, these are AppleInsider, thefreeidctionary that actually work. But that's a different topic.