When you mention Standby server, is it the 2nd node of the UCCX - HA Cluster (2 Node Cluster). Cisco UCCX does not support Mixed Mode authentication, uses only NT Authentication, which is setup by the Custom SQL installation provided by Cisco. You might face sync issues doing the change, as well TAC might not support in case of issues.
You can perform a workaround using the NT authentication:
Create a user on both the UCCX server using Computer Management. Add the user to the Administrative group.
Create the same user with same password on the system from which you want to access the SQL Reporting services on a separate machine.
Test the access to the UCCX SQL DB using the ODBC connection from the separate machine.
HTH