We are told that the album features all new compositions.
Now I'm just playing the devil's advocate here, but do you think that there may be any old (unheard) tracks that they had bits from years gone by where they had started ideas with Freddie, but have now thought, "well we can revisit that idea", and so have worked on old "Queen" stuff with Paul? I know Brian is very much someone who goes back to old ideas (see both his solo albums which were recorded over a number of years, and revisited old demos of his).
It will be interesting to see if anything that we hear with Paul crops up in demo form in any future Queen Anthology!