Yeah its true. Here's the August 2013 Entertainmentwise article reporting on it and an excerpt from said article reads
Under the US Copyright Act, Sir Paul will be able to claim the titles and earn royalties and licensing money in five years time. The Act means songs written prior to 1978 turn into the property of the songwriter after 56 years, meaning the 71-year-old star will regain the majority of his hits by 2026.
I don't quite get how it works tho. Since its US copyright laws does this mean its only applicable in the US and so Paul wont own them in the ...