As always, it depends
First, a couple tidbits about lead acid batteries:1. Heat can permanently damage a lead acid battery. A cold battery simply has a reduced available capacity. It's unlikely that cold by itself has permanently damaged your batteries.2. Sulfation is caused by repeated shallow discharging. Your batteries very well may be sulfated but it wouldn't have come from improper storage. I'd suggest one or two rounds of equalization before giving up on them.3. Lead acid batteries do self-discharge. The rate can be from 3 - 10% per month depending on construction, condition and antimony content of the plates. You don't say how long yours were stored but it's a good bet they were pretty heavily discharged if you're talking about 6+ months. Whether they were permanently damaged by this would be hard to say.As for holding the yard liable, that's a tough call. If your agreement with them specifically called for battery removal and a multi-stage charging for the duration I'd say go ahead and and bring it up and see what they say. If not, well, they're your batteries and you've learned some valuable lessons.