Actually you may have trouble integrating with Sonar. The Sonar Surefire sensor will successfully find your surefire reports; however, the sensor attempts to link to the test source for publishing to Sonar. When it does this, it assumes a file extension of .java. So you will see output in your build that looks like this:
[INFO] [13:00:34.734] Sensor SurefireSensor...
[INFO] [13:00:34.735] parsing /home/amcdowel/accurev/projectFoo/target/surefire-reports
[WARN] [13:00:34.747] Resource not found: com.abc.monitor.app.model.MonitorTest
The code coverage generated by your Spock tests will successfully be reported in your Sonar dashboard, but the number of unit tests and success/error counts will not be included.