As I understand it, the last Fire Boat operated by the City of Milwaukee, was taken out of service in or around July, 1990. The last remaining Fire Boat Station was located on Water Street right at the bridge. You can go over their current equipment list and building locations here:
It is possible that the Gillen Tugboat Company may have a deck water canon and pump on one of their larger tugs, but I was unable to confirm this through two or more sources, so that is only a possibility. The US Coast Guard operates marine firefighting equipment out of their facility. You can read about their protocols and firefighting/rescue plan in the Milwaukee area here in this Microsoft WORD format file:
Milwaukee still has thier own fireboat. Callsign is Fireboat Phoenix. It is houseed at 100 West Virgina Street in Milwaukee along with the Milw. Dive Team, the inflatable fireboat "The Zodiac" , and Engine 3.