Board Thread:Spoilers!/@comment-1916997-20151016201626/@comment-5899967-20151017161224

Farerb wrote: When they say "can't say" it means they didn't plan it and they don't know.

Not really, you have to read it and interpret it, it varies on the question. For example:

"Did Emma (Jennifer Morrison) cast the curse herself? EDWARD KITSIS AND ADAM HOROWITZ: Can’t say."

Here, I think it means "no".