If you configure from passive-serial (e.g. "user" or "safe" design): you can't access the EPCS4, even if your configuration contains the ASMI peripheral (ASMI access routines return the error code "na_asmi_err_device_not_present").
If you configure from JTAG or EPCS4: you can access the EPCS4 if your design contains the ASMI peripheral, as you'd expect.
If you configure from JTAG or EPCS4: you can access the EPCS4 if your design contains the ASMI peripheral, as you'd expect.