There seems to be a decent mix of antennas on ISP vehicles aside from the "standard" Motorola 700/800 MHz which is the Maxrad BMAX7603S. Around here it's usually a 1/4 wave VHF antenna and a shorted 1/4 wave antenna for the MDC. At least one of the MCS SUVs has a Laid WPD136M6C-001 which is a VHF/UHF/800 antenna. Others have a Firestik or the like CB antenna as well.
At the Chicago auto show a couple years back the Dist. 15 car they had on display had 3 Sti-Co flexi-whip antennas cut to various lengths.
Long story short, the antenna with the spring and the open coil in the middle is the BMAX7603S