You can pretty much forget about service to Boise from the East unless someone finds the money to restore the track that was used by the Pioneer to get to Boise from the east. That track was abandoned a while back. All you will get is a stop in the middle of nowhere with a bus connection to Boise, somewhat like Maricopa for Phoenix or in the past Borie for Cheyenne.
One a daily Portland-Boise-Salt Lake City run that runs through Idaho in Daylight(what a novel idea, have at least one Amtrak train pass through during the day, might get some good ridership), and another timed to connect with the California Zephyr in Denver.
...except that Maricopa never had a bus connection with Phoenix. Passengers are on their own to get to and from the station in Maricopa.
Does the UP mainline go through Nampa? If so instead of a station stop in the "middle of nowhere" they could stop in Nampa. A regional bus company has service between Nampa and Boise: http://www.valleyride.org/