I can't remember if I ever read whether Tadd was happy about Bill Evans playing on The Magic Touch album. I think, IIRC, he did denigrate his own "arranger's piano" style somewhat, but I don't remember whether the decision to use another pianist was Keepnews' or Tadd's.
I love the way he used the underrated John Collins as a featured soloist on the Capitol recordings and Royal Roost engagement, especially on the April in Paris chart originally recorded by Hawkins.