If they can control the valves used by the system, sure. If I remember correctly most are 24v AC valves. So if a relay switch could handle that it could easily set the valve on/off. Or more regular modules could turn the power supply on/off as needed. There are usually workarounds available to most things, especially if you can do some DIY... The problem is that it usually does not look as nice, may not be as robust, etc...