Did NMDOT historically not use a lot of VHF for communications? Why do they mostly use cell phones in some districts?
Most the work is scheduled in morning, work orders so everyone knows where what crew is where and there is very skeleton crews at that per district. Though there is rural subs that have cruisers which is known now who skate by all day making it a adventure or sight seeing day unless something comes in from the district head office. Most the use of the radio is during storm events such as plowing or traffic control on simplex car to car off the microwave channel between another or big events where needed or cell use is impossible on the microwave end which isn't common.
Mostly though depending where you are at user preference as this opinion varies between them and how the sub district supervisor feels about it or enforces use or not of the microwave vhf channels, or local repeated if applicable for that district sub station.
There is some who do use it mostly in North.
I know for fact majority of the techs for nmdot lack radio equipment due to budgets or it not being made a priority and some wanting them but it not being made a priority. If they are lucky old supervisor trucks or hand me downs from maintenance end make it to the techs with a radio already and left in though it isn't a common occurrence as they typically get new fleet issued vehicles. Handheld in use are few and simplex mainly for traffic control close range. Most the use is mobiles if used at all.
Have talked with some who are attempting to make this a issue to get it standardized for nmdot. Public works in NM is a for the most part in majority of places a joke or cash cow with its management for public safety monies. A lot of public safety gets money from the public works budgets floated over to them. So is made last priority when it comes to communications.
At one time low band was used heavily back in the day before cell phones. Once cell phones hit your management or requirement of 2 way use went down hill with most public works.