It depends... mostly on how the property was acquired and what the purpose was for acquiring it. If it's land acquired for the public trust (use by the general public), then it has a claim of sovereign immunity. If it's acquired for a corporate use (county shops, etc) no sovereign immunity might not apply. Is it owned by the public, or owned by a corporation for business use?
You could also try looking at the estoppel doctrine. It appears that there is evidence of recognition by a municipality of the private party's ownership. Can get pretty fact intensive.
JBStahl, PLS, CFedS
***May your Boundaries Fall in Pleasant Places*** Ps. 16:6