If they had a live transformer in an area that is confining, I'd think seriously about contacting OSHA. They have some serious rules about fencing them off to limit the possibility of someone contacting it, as you did. For them to have stuff stacked around it, just adds to the seriousness.
I think, that dropping the "I'm gonna call OSHA to see what they say about where the transformer was" will go a long way toward making them drop their claim for damages. If the transformer was put there by the utility company, shame on them.
If it was up on a pole, it would have been different. But, for it to be "on the ground", just isn't right. No fencing. No barriers. Not right. I guarantee that OSHA has rules on it. Check
www.osha.gov for the ruling that they should be following.