They might not be dispatched by anyone in particular, or could be dispatched somehow by Lakeside Police Department through unknown means, and they only respond to calls on the Lakeside Amusement Park grounds. They probably use one of the frequencies off of KSW929 to communicate with 453.750 MHz, 460.150 MHz, and 460.275 MHz being listed as repeater outputs. The RadioReference Database has 453.750 MHz as being DPW, but I believe that is actually used for park operations and it would not be surprising if they used it for their fire department communications as well since the park employees are also the firefighters.
Ambulances are provided by West Metro Fire Rescue if requested by the park. The rest of Lakeside that is not the park is covered by West Metro Fire Rescue.