If that is local law or utility company policy, you have nothing to fight... just pay it and learn the lesson.

Then he started running late, three months in a row and was fighting me about late fees, 3-day Pay or Quit Notices, etc.

You filled out a sellers disclosure and they can and will use anything in that against you and they will probably say you did not do a good job repairing the roof, I assume you will probably win in a legal battle but how much will it cost you to fight it?

No fighting.  

Obviously since this family just lost the property they likely cannot fight for the shed even though it sounds like it's theirs. 

That being said, you should probably ask yourself whether these repairs are necessary before you fight them on it.

I suspect every creditor would like to go over the LL for bills that they cannot collect from the tenant, but that is silly and not the LL's responsibility.I recognize that fighting items has a cost, but seriously I question what the utilities argument would be for charging the LL for utilities that they did not use and is not in their name.Good luck

About 10 years ago counties got sick of fighting people over the values and the taxes.

People know this and they give up fighting, it is just something that has gone on for too long and the general feeling is that this unacceptable situation cannot be changed in the short term. 

I hired Bill Wantz who used to be the hearing officer over the kangaroo "court" that hears the appeals of the notices to fight every single one they give me now.