I believe that analog cellphones were made to operate in the 869-894 MHz range. While you might be able to get them to receive in the somewhat lower frequencies used for trunked public service communications, it seems pretty unlikely that you'd be able to get them to follow those trunked systems. Getting them to scan as we expect from a dedicated scanner seems even less likely since they were designed to move from frequency to frequency in response to computer instructions rather than to move through a series of frequencies looking for one that is active to listen to. If anything, I would think that they'd be looking for one that wasn't active.
In any event, let us know if you have any success. I've been wrong before and perrhaps I'm being unduly pessimistic about this.
Since they transmit as well as receive, you might want to exercise some care that you don't accidentally end up interfering with legitimate communications.