Yes, its possible. Do you have access to the help files on the system as they are very good.
You will have to change the class of service for the sets probably. To allow Silent Monitoring, enable ACD Silent Monitoring - Allowed in the supervisor's Class of Service and enable COS option ACD Silent Monitoring - Accept for the agents or at least one member of the hunt group.
1) Monitoring Individual ACD Agents or Non-ACD Sets
SUPERSET 420, SUPERSET 4025, SUPERSET 4125, SUPERSET 4015 telephones, 5010 IP Phone, 5207 IP Phone, 5212 IP Phone, 5215 IP Phone, 5215 IP Phone (Dual Mode), 5020 IP Phone, 5220 IP Phone, 5224 IP Phone, 5312 IP Phone, 5320/5320e IP Phone, 5324 IP Phone, 5330/5330e IP Phone, 5340/5340e IP Phone, 5360 IP Phone, Navigator, and 5230 IP Phone, and Symbol Wireless Phones:
To use silent monitor on an individual ACD agent or non-ACD set:
Lift the handset.
Dial the Silent Monitor feature access code followed by agent's ID or the directory number of the non-ACD set.
SUPERSET 430 Telephones, SUPERSET 4150 Telephones, 5235 IP Phone
To use silent monitor on an individual agent:
Press ACD.
Press Monitor.
Dial the agent's directory number or the directory number of the non-ACD set.
Press Enter.
Feature code will be whatever is set in your feature code list.