There is also a thread about this in the Federal monitoring forum, this is how it works now. National Park Service has a wild land fire station in Boulder City, NV. They use the Boulder LE frequency, 170.050 analog, when operating in the park, switch to other freqs. when dispatched out of the area. Supervisor's call signs 7300-7302, engines are 7361, 7362, sometimes a squad or patrol are also heard. They also respond to assist the NPS rangers with SAR calls and major incidents.
LMNRA used to operate structure fire engines in each of their major districts in NV and AZ but in recent years haven't had rangers certified in structure fire operations to man the apparatus. It's unknown how many engines remain in the stations, if any. Mutual aid from nearby agencies is now requested for fire calls, for example Clark County, Henderson, Boulder City in NV and Mojave Ranchos, AZ. Those agencies use their own radio systems. Mutual aid works but the response time is longer. NPS also has a fairly new fireboat based in the Boulder Basin, call sign Fireboat Brown, which they do man and use for SAR as needed.
EMS is a little different. The NPS has a couple of ambulances and a medic SUV manned by two paramedics, Medic 41 and Medic 42. The paramedics, with the SUV and one ambulance are based at a former fire station near the Boulder Beach ranger station. The ambulance used to be identified as Rescue 4 (Boulder Beach area is district 4) but now is identified as Rescue 1. Some of the NPS rangers are EMTs and respond on medical calls as well. Medical calls are dispatched on the Boulder LE frequency. Hospital transports when needed are usually done by Community Ambulance from Henderson or the nearest fire district paramedics. Air ambulance service by Mercy Air in NV and various air ships in Arizona. Medical air to ground coordination is usually on the NPS admin. freq.166.300.
Hoover Dam fire and EMS is handled by Boulder City Fire. NPS rangers provide law enforcement there now as the Hoover Dam federal police department was stood down about two years ago. The relatively short range VHF P25 radio system (163.125) at the dam is still used by security guards and occasionally by the NPS rangers.