AZ State/Mohave County don't seem to have a lot of high profile LMR sites near the Hoover Dam area border that makes it over the mountain range into the Henderson/Las Vegas area -- seems like they chose sites --at least high profile/ERP ones-- relatively far south in AZ. Best evidence of this in my opinion is how difficult it can be to hear the local AZ DPS Highway Patrol UHF repeater & Mohave SO area dispatch in Boulder City, even though the Arizona-side of US-93 is so close.
In other parts of the Henderson/LV area, Mohave County seems to come-in pretty well on 155.640/192.8 & 153.935/186.2