Trainweb article by Tom Jones: Milwaukee Road in the 70's: What really happened?
Motorbooks International book by Tom Murray: Save Our Railroad Employment
S.O.R.E.'s motion to intervene in CMStP&P bankruptcy proceedings, 1979
Hopefully this is a good start for you - the Trainweb article is the most sensationalist, but also has the best narrative on why the lines should have been saved.
EDIT: The Milwaukee Road Archives has an entire section on Milwaukee Road bankruptcy
, as well as the SORE, New Milwaukee, and Montana Pacific proposals to continue operation of the westernmost Milwaukee lines, ending with the final court case to decide why the C&NW, despite bidding a higher amount for the MILW, was not preferable to the Soo Line's bid.