Is it possible to use the sensorProbe2 to shutdown a series of three servers in a small server room?
Not directly or easily. None of the sensorProbe series products support switching off servers directly. It could be possible to send an email to a server and then have a job on the server wait for alert emails and then trigger the shutdown script.
The securityProbe range provides a more direct solution as it is has a feature enabling it to shut down one or more servers. There is also a notification wizard for configuring the alarm actions. In this case you would need a temperature sensor, the alarm could then be configured to execute a series of shutdowns when the temperature goes above a given threshold.