http://www1.control.com/1026223377/index_html#1026223473
"If you are using the other processors (620-06, 10, 15, 25 or 35), there is a modbus module which can be added to the I/O rack. I believe that this will require the addition of coding to place the desired information in the module."
Once you're talking Modbus RTU, then any Modbus RTU OPC server (Kepware, Matrikon, Softing) should work.
The Honeywell IPC 620 product line reflects the Honeywell continuing commitment to deliver proven logic control to specific markets that tie together in all segments of industrial control technology. Other members of this family are: 620-2590, 620-35, 620-3590, 620-25/35, 620-0080, 620-25/35, 620-0054, 620-0025.