I'm not in Brooklyn enough to hear whether "blabbity blah" is a common expression.
From the mouth of Brooklyn resident Alex Basek, as quoted in the July 26 New York Observer article "A Twee Grows in Brooklyn":
“There’s Glass Shop, a fancy coffee spot, like single roaster blabbity blah, all the way on Classon Avenue."
It certainly doesn't make me think of Babbitty or even blabber. Possibly blubber. And maybe the verb blab.
Winningly, it has summoned from the depths of memory a phrase I once liked very much, viz., "blather blather."
Blabbity blah has more kick.
Mostly it makes me think about how seldom I hear people say this. Could be that the emphases work out well, though--a little like dickory dock. Blabbity wouldn't be the same if it were flying solo.