There are several key issues that are undecided by the court. The most notable is who owned the common-law copyright (or the first right to publish) the lyrics. It's unclear in this instance, but the presumption is that it's the Hill sisters.
Whoever owned that copyright continued to do so until first (authorized) publication or January 1, 1978, where it follows the rules (most likely from first creation, since it's an expires-first rule). The expiration is the death of the last author + 70 years (2016, if the Hill sisters created it) or 120 years from at most 1911 (if it's anonymous, since we know it had to be created before 1911 by a (presumably unauthorized if this is to apply) publication).
If there was an authorized publication, then it's public domain if there's no copyright notice. If there's a copyright notice, then it's still copyrighted today only if all the rules were followed, which is pretty unlikely at this point. The existence of the 1922 Everyday Song Book may or may not constitute this publication, and the notice may or may not constitute a legal copyright notice (it was never decided by the judgement, only that the question requires a trial to determine the answer).
From the record, it seems likely that the Hill sisters owned the copyright, but considered it abandoned and so never actually published it. However, they probably didn't actually legally lose their copyright, so it follows the 1976 copyright act rules, which means that the copyright is now held by their heirs and will expire next year. Of course, if said heirs wish to try to enforce the copyright, they will have to actually prove all of the findings of fact to make it the case, which is probably not worth the burden given the time left.