The PRO-74 is not a trunktracker, the best I remember. To get anything on the Richardson EDACS system just program the Richardson Frequencies as normal. It may be hard to follow complete conversation or communications. Richardson also uses 868.6125 as a Fire Toneout frequency
Radio Shack and Uniden, both make good scanners. For trunking you can except to pay anywhere from $150.00 to $500.00+ for a scanner. Check out Radio Model Information of the wiki section. For a Radio Shack model you might look at the Pro-97 / Pro-2055 and the PRO-96 / Pro-2096 (digital). Use an outside antenna to increase what you can receive.