I'm not saying this would work for scanners, but back in the early days of CATV (When CATV stood for Community Antenna TV), one way used to get TV signals into a valley when the surrounding hills or mountains blocked the broadcast signal was to place a TV antenna on top of the mountain where it could pick up the broadcast signal and connect it to another TV antenna pointed down into the valley where the viewers were located. These "passive repeaters" didn't require any power, and made it possible for isolated communities to get TV reception, whence the Community Antenna name.
Would something like this work for scanners? I don't know. Coax line loss might eat up the signals. The antennas referred to above were closely mounted and connected. Maybe somebody will give it a try.
Mark S.