Bishop Finn appoints away some episcopal authority. Or does he? In the old days (of JPII) it was Rome who appointed co-adjutors to ride to the rescue. In the 21st century, I guess this is left to western bishops to work out their own messes.
David Gibson has the piece up at both RNS and dotCommonweal.
Jack Smith, diocesan newspaper editor and once-active blogger, explains:
Fr. Rush’s sole responsibility is to make decisions with regard to resolving a misdemeanor charge against the diocese in Jackson County. In all but this matter, Bishop Finn continues in all of his duties.
There is a perceived conflict that this helps resolve. Bishop Finn and the diocese each have been charged with identical misdemeanors in Jackson County. It is possible that the defense or resolution of one charge could be in conflict with the defense or resolution of the other charge. For this reason a Vicar has been appointed with authority to independently represent diocesan interests with regard to the charge against the diocese.
So it seems less a matter of canon law and more one of secular legality.
I see my friend Msgr Murphy has returned to full-time parish ministry–no more VG work for him. That should be a relief to the man. I always had a sense he saw the role of the priest–his own best, gifted role–was as a parish pastor. While I have no particular inside knowledge on this situation, I do know that Bishop Finn kept his own counsel on priest appointments. If he had made up his mind that any offending priest could be rehabilitated, no number of committees or clergy could sway his judgment.
Catholic Sensibility 
Finn seems to make up the rules as he sees fit, to protect himself, and keep himself out of jail.
Judy Jones, SNAP Midwest Associate Director, 636-433-2511
If he wants to wear the crown then he has to bear the cross.
Even if he is ontologically favored.