Earl,
I have never seen anything in writing prohibiting the Big Brooks consolidations from running up the Clear Creek lines. According to some authors, the last Employee timetable that was used was from 1922 and all modifications were made via Superintendent's Bulletins. I do know that when the C&S looked at purchasing that ex-Uintah 2-6-6-2's that one of the reasons that it was not done was because the bridges on the Clear Creek Lines were too light to handle them.
Since the 74-76 were handling the South Park traffic so well and with little problem, it seems that the logical thing would be to keep them there and use the 70 on Clear Creek rather than using those big Brooks and having them end up in the middle of Clear Creek. Of course, the is a problem here and that is that the use of Railroad and Logic in the same sentence is an oxymoron for anybody who has worked for one.
Rick