Even if you could, there wouldn't be much point anyway, all you'd actually be able to recieve are the group calls that go out occasionally, but they're mostly just about lost property, with the occasional warning about concession cards/passengers or message about diversions. You wouldn't be able to listen in to calls between control and individual buses.
When I worked on the buses in Newcastle years ago they upgraded the radio system to digital in the early 90's as I seem to recall there was a revision of the band used. Band II to band III or something like that anyway, so an upgraded system was installed and the old Storno system removed.
So .....no you cannot unfortunately.