Undoubtedly Steve Thomas told Donald Foster about The Prime of Miss Jean Brodie's connection to Patsy. In Death of Innocence, we're told that Thomas questioned Patsy's friend Linda McLean about Patsy's dramatic readings. Foster would have discovered the references to the spelling of possession, the mention of attache' cases, etc. (It's unlikely, though, that Foster would ascribe much significance to pineapple. People don't eat pineapple because it's mentioned in The Prime of Miss Jean Brodie.) These observations would have made it into Foster's report along with other original observations we know about such as Patsy's penchant for acronyms and exclamation points, the appearance of and hence in the Ramsey 1997 Christmas letter, possible sources for the $118,000 in the ransom note, Patsy's two different kinds of a's and how those "a's" changed, Patsy's change to writing etcetera when she had always written etc. before and, of course, Foster's discovery of the origin of SBTC in Psalm 35 in the open Bible in the third floor study.
But as far as the observations about The Prime of Miss Jean Brodie in blogs on the internet, these seem to be wholly the original product of Brothermoon/Red Dragon. Putting them in a book without Brothermoon's permission would be unethical. It might also be illegal since there might be an implied copyright.