Sara,
As suggested, I most definitely would contact Citizens Energy Group. I too have never heard of Citizens taking responsibility for such damage. From a legal standpoint, below are suggestions:
1. Reread your signed Property Management Agreement as to your PM's fiduciary duties to you as the client. It sounds like you may have a breach of contract and negligence action.
2. Demand the contact information at Citizens to speak with them directly as to what happened, etc. Confirm the information you are being told by the PM is accurate.
3. Gather all specific details as to matter. Specifically, as to when utilities were shut off. Who called in to the work order? It probably was the PM. Request a copy of the work order. Get specific name of Citizens representative who went to the property and shut off the water. Was it actually a Citizens employee or one of their contractors? This makes a difference.
4. When did the PM become aware of it? Had they shown the property? Request a copy of their specific records.
You need to start building a legal case here, even if no legal action is required. Just some helpful tips. I have represented clients on matters similar to this when it comes to potential PM negligent actions.
In the future, you may want to fax a letter to Citizens requesting that when any tenants move out that all utilities revert back to you, the Landord, automatically. I have this on all of my rental properties and this has proven to be most helpful! Especially when tenants skip out on you before you can get ahead of them.