In 14.1 the option to Report Noise Analysis for Spartan-6Q is present but does not generate the report.
SSN reporting for a corresponding non-Q Spartan-6 part functions as intended.
SSN analysis is not supported for the Spartan-6Q parts and the option should not have been enabled in PlanAhead tool.
The best solution to get usable SSN information for a Spartan-6Q design is to run SSN analysis while targeting the corresponding non-Q Spartan-6 commercial part. Then de-rate the commercial part by 20% and you should get a similar margin.