Notwithstanding RSA 507-B:2, a governmental unit shall not be liable for damage arising from insufficiencies or hazards on any premises owned, occupied, maintained, or operated by it, even if it has actual notice of them, when such hazards are caused solely by snow, ice, or other inclement weather, and the governmental unit’s failure or delay in removing or mitigating such hazards is the result of its implementation, absent gross negligence or reckless disregard of the hazard, of a winter or inclement weather maintenance policy or set of priorities with respect to such premises, adopted in good faith by the official responsible for such policy. All governmental units, officials, and agents shall be presumed to be acting pursuant to such a policy or set of priorities in the absence of proof to the contrary.