When permitted by law to transfer any of its functions or services to, to lease its property to or to perform any function, service or act with or for any other local public entity or employee thereof by agreement with such other local public entity, a local public entity may agree with the other entity as to the manner in which liability for an injury resulting from such function, service or act is to be allocated or shared. Such agreement may be expressed by resolution, contract, lease, ordinance or in any other manner provided by law.