Basically, the county is asking the city to provide 500 beds (this has been an ongoing debate). The city claims to not have them. In addition to that, though, the county is asking the city to pay 20 million for the land, which was appraised between 10 and 12 million. There was another article about this recently, saying that land prices have risen well beyond the estimates for beltline land due to speculation. The city is understandably irritated, because land is being sold to them for well over the estimated tax value, meaning they are paying more than they budgeted for (whats new?) and they aren't getting that additional tax.
Essentially it seems the county is pulling a power play, because they know the city wants to buy the land, and ther was much fanfare over the quarry-turned-park.